EXHIBIT 4.3(a)
 
                    AMENDED AND RESTATED CREDIT AGREEMENT dated as of November
               25, 1997, as amended and restated February 5, 1999, among
               EQUISTAR CHEMICALS, LP, a Delaware limited partnership;
               MILLENNIUM AMERICA INC., a Delaware corporation, as Guarantor;
               the Lenders party thereto; BANK OF AMERICA NATIONAL TRUST AND
               SAVINGS ASSOCIATION as Servicing Agent, Documentation Agent and
               Administrative Agent; and THE CHASE MANHATTAN BANK, as
               Syndication Agent and Administrative Agent.

          WHEREAS, the Borrower (such term and each other capitalized term used
but not defined herein having the meaning assigned to it in the Credit Agreement
as amended and restated hereby, the "Amendment and Restatement"), the Lenders,
BofA and Chase are parties to the Credit Agreement dated as of November 25, 1997
(the "Credit Agreement");

          WHEREAS, the Borrower has requested that the Lenders amend and restate
the Credit Agreement; and

          WHEREAS, the undersigned Lenders are willing, on the terms and subject
to the conditions set forth herein, to approve such Amendment and Restatement;

          NOW, THEREFORE, in consideration of these premises, the Borrower,
Millennium America Inc. and the undersigned Lenders hereby agree as follows:

          SECTION 1.  Amendments.  Effective as of the Amendment and Restatement
Effective Date (as defined in Section 3 hereof), the Credit Agreement is hereby
amended and restated in its current form with the following amendments:

          (a)  The following definitions are added to Section 1.01 of the Credit
Agreement in their appropriate alphabetical positions:

               "Assumed Occidental Liabilities" shall mean amounts due under the
     Lease Intended for Security, Corpus Christi Ethylene Cracking Facility,
     dated December 18, 1991, among Oxy Petrochemicals Inc., as assignee of
     Occidental Chemical Corporation, as Lessee, the institutions listed on the
     Schedule I thereto, as Lessors, Norwest Bank Minnesota, N.A., as Agent and
     Chemical Bank and the Bank of Nova Scotia, as Information Agents, as
     amended and supplemented from time to time.

               "Equistar GP" shall mean any general partner of the Borrower.

               "Occidental Asset Contribution Agreement" means the Agreement and
          Plan of Merger and Asset Contribution dated as of May 15, 1998, among

 
                                                                               2


          Occidental GP, Occidental LP1, Occidental LP2, Oxy Petrochemicals Inc.
          and the Borrower.

          (b)  The definition of "Applicable Percentage" in Section 1.01 of the
Credit Agreement is hereby amended by (i) replacing the table contained therein
with the following table:

                                                   Facility        
           Index               LIBOR/NIBOR           Fee   
          Ratings                 Spread          Percentage 
          -------              -----------        ----------

Category 1                         .285%            .090%
   A-/A3 or higher
 
Category 2                         .375%            .125%
     BBB+/Baa1
 
Category 3                         .475%            .150%
     BBB/Baa2
 
Category 4                         .675%            .200%
    BBB-/Baa3
 
Category 5                         .775%            .225%
    BBB-/Ba1 or BB+/Baa3
 
Category 6                        1.000%            .250%
    BB+/Ba1

Category 7                        1.200%            .300%
    BB/Ba2 or lower
- --------------------------------------------------------

(ii) replacing the number "6" at the end of clause (i) thereof with the number
"7" and (iii) inserting immediately before the semicolon at the end of clause
(ii) thereof the following: "(except that for purposes of this clause (ii),
Category 5 shall be disregarded in determining the number of Categories by which
the Index Ratings differ)".

          (c)  The definition of "Change in Control" in Section 1.01 of the
Credit Agreement is hereby amended by replacing the definition in its entirety
with the following:

               A "Change in Control" shall occur if at any time Lyondell,
     Millennium and Occidental cease to own in the aggregate, through ownership
     by one or more of them, partnership interests representing at least a
     majority of the total equity interest and voting power of the Borrower.

          (d) The second proviso in the definition of "EBITDA" in Section 1.01
of the Credit Agreement is hereby amended to read as follows:  "provided
further, that after December 31, 1998, such addition may only be made in the
calculation of EBITDA for each of two fiscal quarters during the remaining term
of this Agreement and any such addition may only be made for one fiscal quarter
during any four consecutive fiscal quarters."

 
                                                                               3

          (e)  The Interest Coverage Ratio in Section 6.05 of the Credit
Agreement is hereby amended by inserting at the end thereof, the following:
"except that for any period of four consecutive fiscal quarters ending on any
date set forth below, the Interest Coverage Ratio shall not be less than the
ratio set forth below opposite such date:

Date                                          Ratio
- ----                                          ------  
March 31, 1999. . . . . . . . . . . . . . . .2.50 to 1.0
June 30, 1999 . . . . . . . . . . . . . . . .2.25 to 1.0
September 30, 1999. . . . . . . . . . . . . .2.00 to 1.0
December 31, 1999 . . . . . . . . . . . . . .2.00 to 1.0
March 31, 2000. . . . . . . . . . . . . . . .2.15 to 1.0
June 30, 2000 . . . . . . . . . . . . . . . .2.25 to 1.0
September 30, 2000. . . . . . . . . . . . . .2.50 to 1.0
December 31, 2000 . . . . . . . . . . . . . .2.75 to 1.0

          (f)  Section 10.15(a) of the Credit Agreement is hereby amended by
replacing "Lyondell GP or Millennium GP, or any of their Affiliates" with "any
Equistar GP or any of its Affiliates"

          (g)  Section 10.15(b) of the Credit Agreement is hereby amended by
replacing all the text immediately after the first sentence thereof with the
following:  "The Occidental Asset Contribution Agreement contains provisions
under which the Borrower would be obligated to reimburse Occidental for any
amounts paid by Occidental or its Affiliates on account of the fixed rent,
purchase obligation and variable rent on the Assumed Occidental Liabilities.
The Lenders acknowledge and agree that the obligations of the Borrower in
respect of any such reimbursement obligations will rank pari passu with the
Obligations"

          SECTION 3.  Effectiveness.   This Amendment and Restatement shall
become effective as of the date (the "Amendment and Restatement Effective Date")
when the Administrative Agents (or their counsel) shall have received copies
hereof that, when taken together, bear the signatures of the Borrower and the
Required Lenders.

          SECTION 4.  Amendment and Restatement Fee. The Borrower shall pay to
the Administrative Agents on the Amendment and Restatement Effective Date a fee
as separately agreed to for the account of each Lender executing this Amendment
and Restatement.

          SECTION 5.  Applicable Law.  This Amendment and Restatement shall be
construed in accordance with and governed by the law of the State of New York.

          SECTION 6.  No Other Amendments.  Except as expressly set forth
herein, this Amendment and Restatement shall not by implication or otherwise
limit, impair, constitute a waiver of, or otherwise affect the rights and
remedies of any party under, the Credit Agreement, nor alter, modify, amend or
in any way affect any of the terms, conditions, obligations, covenants or
agreements contained in the Credit Agreement, all of which are ratified and

 
                                                                               4

affirmed in all respects and shall continue in full force and effect.  This
Amendment and Restatement shall apply and be effective only with respect to the
provisions of the Credit Agreement specifically referred to herein.

          SECTION 7.  Counterparts.  This Amendment and Restatement may be
executed in two or more counterparts, each of which shall constitute an
original, but all of which when taken together shall constitute but one
contract.  Delivery of an executed counterpart of a signature page of this
Amendment and Restatement by facsimile transmission shall be as effective as
delivery of a manually executed counterpart of this Amendment and Restatement.

          SECTION 8.  Headings.  Section headings used herein are for
convenience of reference only, are not part of this Amendment and Restatement
and are not to affect the construction of, or to be taken into consideration in
interpreting, this Amendment and Restatement.

          SECTION 9.  Expenses.  The Borrower shall reimburse the Administrative
Agents for their reasonable out-of-pocket expenses incurred in connection with
this Amendment and Restatement, including the reasonable fees and expenses of
Cravath, Swaine & Moore, counsel for the Administrative Agents.

          IN WITNESS WHEREOF, the Borrower, Millennium America Inc. and the
undersigned Lenders have caused this Amendment and Restatement to be duly
executed by their duly authorized officers, all as of the date first above
written.



                                        EQUISTAR CHEMICALS, LP

                                           by /s/ Eugene R. Allspach
                                             ----------------------------
                                             Name: Eugene R. Allspach

                                             Title: President and Chief
                                                     Operating Officer


                                        MILLENNIUM AMERICA, INC.

                                           by /s/ Christine Wubbolding
                                             ----------------------------
                                             Name: Christine Wubbolding

                                             Title: Vice President and
                                                     Treasurer

 
                                                                               5


                                        BANK OF AMERICA NATIONAL TRUST      
                                        AND SAVINGS ASSOCIATION,            
                                        individually and as                 
                                        Administrative Agent, Documentation 
                                        Agent and Servicing Agent,          


                                           by /s/ Michael J. Dillon
                                             ----------------------------
                                             Name: Michael J. Dillon
                                                  
                                             Title: Managing Director 



                                        THE CHASE MANHATTAN BANK, 
                                        individually and as       
                                        Administrative Agent and  
                                        Syndication Agent,         

                                           by /s/ Mary Elizabeth Swerz
                                             ----------------------------
                                             Name: Mary Elizabeth Swerz

                                             Title: Vice President


                                        ABN AMRO BANK N.V.,
                                           by /s/  Collis G. Sanders
                                             ---------------------------- 
                                             Name: Collis G. Sanders

                                             Title:Senior Vice President
                                                   & Managing Director

 
                                           by /s/  Gordon D. Chang 
                                             ----------------------------    
                                             Name: Gordon D. Chang

                                             Title: Vice President

 
                                                                               6


                                        BANK AUSTRIA AG,

                                           by /s/  R. Tenhave
                                             ----------------------------
                                             Name: R. Tenhave

                                             Title: Senior Vice President

                                              /s/  Karen L. Jill
                                             ----------------------------
                                             Name: Karen L. Jill

                                             Title: Assistant Vice President



                                        THE BANK OF NEW YORK,

                                           by /s/  Raymond J. Palmer
                                             ---------------------------
                                             Name:  Raymond J. Palmer

                                             Title: Vice President



                                        THE BANK OF NOVA SCOTIA,

                                           by /s/  F. C. H. Ashby
                                              -------------------------
                                              Name:  F. C. H. Ashby
 
                                              Title: Senior Manger Loan 
                                                       Operations


                                        THE BANK OF TOKYO-MITSUBISHI,

                                           by /s/  Ichiro Otani
                                              ------------------------
                                              Name:  Ichiro Otani

                                              Title: Deputy General Manager

 
                                                                               7

                                        BANQUE NATIONALE DE PARIS,

                                           by /s/ John Stacy
                                             -------------------------
                                             Name: John Stacy

                                             Title: Vice President


                                        CIBC INC.,               
                                        by CIBC OPPENHEIMER CORP, 
                                        as Agent,                 

                                           by /s/  Ihor Zaluckyj
                                             -------------------------
                                             Name:  Ihor Zaluckyj
                              
                                             Title: Executive Director


                                        COMMERZBANK AG,

                                           by /s/  W. David Suttles
                                             -------------------------
                                             Name: W. David Suttles
                                    
                                             Title: Vice President

                                           by /s/ D. L. Ward
                                             -------------------------
                                             Name:  D. L. Ward

                                             Title:  Assistant Treasurer


                                        CREDIT LYONNAIS NEW YORK BRANCH,

                                           by /s/ Phillippe Soustra
                                             -------------------------
                                             Name:  Phillippe Soustra

                                             Title: Senior Vice President

 
                                                                               8

                                        THE DAI-ICHI-KANGO BANK, LTD.,

                                           by /s/  Timothy White
                                             -------------------------
                                             Name: Timothy White

                                             Title: Senior Vice President


                                        DEUTSCHE GENOSSENSCHAFTS BANK AG,

                                           by /s/  Mark Connelly
                                             -------------------------
                                             Name: Mark Connelly
                                         
                                             Title: Vice President

 
                                           by /s/  Elizabeth L. Ryan
                                              ------------------------
                                              Name:  Elizabeth L. Ryan
                                         
                                              Title:  Vice President


                                        THE FIRST NATIONAL BANK OF 
                                        CHICAGO,                   
 
                                          by /s/  Dixon P. Schultz
                                             ------------------------
                                              Name:  Dixon P. Schultz        
                                                                          
                                              Title:  First Vice President 
 
 

 
                                                                               9

                                        THE INDUSTRIAL BANK OF JAPAN,     
                                        LTD.,                             
                                                                          
                                           by /s/  Mike Oakes             
                                             ------------------------     
                                             Name: Mike Oakes             
                                                                          
                                             Title: Senior Vice President 
                                                     Houston Office        
 
 
                                        KBC BANK N. V.,

                                           by /s/  Robert Snauffer
                                             -------------------------
                                             Name:  Robert Snauffer         
                                                                         
                                             Title:  First Vice President 

 
                                            by /s/  Marcel Claes                
                                              ------------------------- 
                                              Name:  Marcel Claes               
                                                                                
                                              Title:  Deputy General Manager


                                        THE LONG-TERM CREDIT BANK OF          
                                        JAPAN, LIMITED,                       
                                                                              
                                           by /s/  Sadao Muraoko              
                                             --------------------------       
                                             Name:  Sadao Muraoko             
                                                                              
                                             Title:  Head of Southwest Region  

 
                                                                              10

                                        MARINE MIDLAND BANK,                    
                                                                                
                                           by /s/  George Linhart               
                                             --------------------------         
                                             Name: George Linhart               
                                                                                
                                             Title: Relationship Manager        
                                                                                
                                                                                
                                        MORGAN GUARANTY TRUST COMPANY           
                                        OF NEW YORK,                            
                                                                                
                                           by /s/  Anna Marie Fallon            
                                             ----------------------------       
                                             Name:  Anna Marie Fallon           
                                                                                
                                             Title:  Vice President             
                                                                                
                                                                                
                                        NATIONSBANK, N.A.,                      
                                                                                
                                           by /s/  Michael J. Dillon            
                                             ----------------------------       
                                             Name:  Michael J. Dillon           
                                                                                
                                             Title: Managing Director           
                                                                                
                                                                                
                                        PNC BANK,                               
                                                                                
                                           by /s/  Marc T. Kennedy              
                                             ---------------------------        
                                             Name:  Marc T. Kennedy
                                                                                
                                             Title: Vice President              
                                                                                
                                                                                
                                        THE SANWA BANK LIMITED,                 
                                                                                
                                           by /s/ Jean-Michel Fatovic           
                                             ----------------------------       
                                             Name: Jean-Michel Fatovic          
                                                                                
                                             Title:   Vice President       

 
                                                                              11

                                        SOCIETE GENERALE,             
                                                                      
                                           by /s/ Karen M. Sager      
                                             -------------------------- 
                                             Name: Karen M. Sager       
                                                                        
                                             Title:  Vice President     
                                                                        
                                                                        
                                        THE SUMITOMO BANK, LTD.,        
                                                                        
                                           by /s/  J. Bruce Meredith    
                                             ----------------------------  
                                             Name:  J. Bruce Meredith      
                                                                           
                                             Title: Senior Vice President  
                                                                           
                                                                           
                                        SUNTRUST BANK, ATLANTA,            
                                                                           
                                         by /s/ M. Anne Ford               
                                           ------------------------------  
                                          Name:  M. Anne Ford              
                                                                           
                                          Title: Corporate Banking Officer 
                                                                           
                                                                           
                                         by /s/  Steven J. Newby           
                                           ------------------------------  
                                           Name:  Steven J. Newby          
                                                                           
                                           Title: Corporate Banking Officer  
                                                                             
                                                                             
                                        THE TORONTO-DOMINION BANK,           
                                                                             
                                           by /s/  Sonja R. Jordan           
                                             ---------------------------     
                                             Name:  Sonja R. Jordan          
                                                                             
                                             Title:  Manager, Credit 
                                                       Administration         
                                                       
                                                       
                                                       
                                        WESTDEUTSCHE LANDESBANK GIROZENTRALE,
                                        NEW YORK BRANCH,                     
                                                                             
                                         by /s/ Felicia LaForgia             
                                           ---------------------------       
                                           Name: Felicia LaForgia            
                                                                             
                                           Title: Vice President             
                                                                             
                                        by /s/  Thomas Lee                   
                                          --------------------------         
                                          Name:  Thomas Lee                  
                                                                             
                                          Title: Associate