December 22, 2004

Phelps Dodge Corporation (PD)


      As you know, Southern Peru Copper Corporation, hereinafter referred to as
SPCC, has been discussing the possibility of entering into a strategic
transaction (the "Transaction") involving Minera Mexico, S.A. de C.V. ("MM").
The Transaction involves MM becoming a subsidiary of SPCC in consideration for
the issuance of Common Stock by SPCC to Americas Mining Corporation ("AMC") for
its approximately 99% MM ownership. The Transaction would involve the
solicitation of votes of the shareholders of SPCC in order to approve the
issuance of Common Stock in connection with the acquisition by SPCC of MM. We
would like to obtain the expression of your current intent to vote to approve
this Transaction in accordance with the paragraphs below.

      We are convinced that the Transaction would transform SPCC into one of the
world's premier mining companies, with superior scale and market position,
high-quality asset portfolio, geographic and country diversification, commodity
and semi-manufactured product diversification, great synergies, sizable combined
sales and EBITDA to compete internationally, and one class of shares to improve
liquidity and access to the capital markets.

Proposed Liquidity and Support Provisions

      AMC is willing to use its reasonable best efforts to cause SPCC to provide
registration rights to Phelps Dodge Corporation, hereinafter referred to as PD,
in accordance with a Registration Rights Agreement that will include the terms
set forth in Annex A to this letter and will otherwise contain terms customary
for registration rights agreements. AMC will use its reasonable best efforts to
cause SPCC to, and PD will, in good faith as soon as possible after the
execution of this letter, negotiate, complete, execute and deliver such a
Registration Rights Agreement.

      In connection with such Registration Rights Agreement and after the
conversion of shares of Class A Common Stock in SPCC held by PD into shares of
Common Stock, PD agrees not to sell its shares of SPCC during the period
beginning on the closing of the Transaction until the end of the Initial Six
Month Period (as defined in Annex A hereto) but in no event to exceed eight
months from the closing of the Transaction, if any, other than through a
secondary offering effected pursuant to the Registration Rights Agreement;
provided, however, that PD shall be permitted to dividend or otherwise transfer
all or any portion of its shares of SPCC to PD's parent corporation, and PD and
its parent corporation shall each be permitted to dividend or otherwise transfer
all or any portion of such shares to the parent corporation's trust shareholders
and/or beneficiaries of such trusts; and provided, further, that such parent
corporation, trust shareholders and/or beneficiaries, as the case may be, shall
first execute one or more counterparts to this letter agreeing to be bound by
its terms.

     During the period described in the prior paragraph, PD agrees that the
maximum number of shares of SPCC that it will sell will be subject to the
volume limitations set forth in the Registration Rights Agreement.

      AMC agrees not to sell and will use its best efforts to prevent its
affiliates shares of SPCC from selling during the during the period beginning on
the closing of the Transaction until the end of the Initial Six Month Period (as
defined in Annex A hereto) but in no event to exceed eight months from the
closing of the Transaction. AMC further agrees to use its reasonable best
efforts to cause SPCC to not conduct a primary offering of its shares during the
first six months following the closing of the Transaction, subject to the
Company's right to issue shares in connection with acquisitions, mergers,
business combinations, applicable benefit plans and other similar transactions.

      Other than pursuant to an offering effected in accordance with the
Registration Rights Agreement, PD will not, following the closing of the
Transaction, knowingly sell PD's shares in SPCC to any strategic buyers or
competitors of the Company without AMC's prior approval, which approval shall
not be unreasonably withheld.

      Taking into account that the Special Committee of disinterested Directors
of SPCC did recommend to the Board of Directors of SPCC the approval of the
Transaction and the Board consequently voted in favor of it, we kindly propose
that PD, together with AMC, express their current intent, and PD and AMC do
hereby express their current intent, to (i) submit their proxies to vote in
favor of the Transaction and for such actions as are required to consummate the
Transaction in accordance with the Special Committee's recommendation and (ii)
take all action reasonably necessary to effect simultaneously with the closing
of the Transaction the conversion of their Class A Common Stock into a single
class of Common Stock with the rights and privileges as set forth in SPCC's
Certificate of Incorporation as it currently exists, which would provide greater
liquidity for all investors.

      This letter will be governed by the laws of the State of New York
applicable to contracts to be performed wholly within such state.


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     We hope you agree that the Transaction is in the best interests of all
of the stockholders of SPCC and we encourage you to sign in the space
provided below to indicate your agreement to the terms of this letter.

                                  Sincerely,

                                  AMERICAS MINING CORPORATION

                                  /s/ Armando Ortega
                                  ---------------------------------
                                  By: Armando Ortega
                                  Title: Secretary
 Acknowledged and Agreed:

 PD

 /s/ S. David Colton
 -------------------------------
 By:
 Title:

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                                                                       Annex A

                 Registration Rights Agreement Term Sheet


Parties                             Phelps Dodge Corporation ("PD") and Southern
                                    Peru Copper Corporation (the "Company").

Shelf Registration                  As promptly as practicable after the closing
Statement                           of the Transaction, the Company will file
                                    with the SEC a shelf registration statement
                                    (the "Shelf Registration Statement")
                                    covering all Company common stock owned by
                                    PD (the "Registrable Securities"). The
                                    Company will use reasonable best efforts to
                                    cause the Shelf Registration Statement to be
                                    declared effective as promptly as
                                    practicable and to remain effective for a
                                    period of at least one year.

                                    The plan of distribution in the Shelf
                                    Registration Statement will contemplate only
                                    underwritten offerings sponsored by the
                                    Company during the Initial Six Month Period,
                                    as defined below.


Demand Registrations                PD will have the right to demand an
                                    unlimited number of registrations of its
                                    Registrable Securities during the first six
                                    months following the effectiveness of the
                                    Shelf Registration (the "Initial Six Month
                                    Period"), provided that the Registrable
                                    Securities sold will be determined by the
                                    underwriters upon consultation with the
                                    Company and PD to be the maximum number of
                                    shares that the underwriters determine could
                                    be sold without causing a significant
                                    disruption in the market for shares of
                                    Common Stock of SPCC and, in any event, at
                                    least 10,000,000 shares.

                                    PD will also have the right to sell
                                    Registrable Securities during the first six
                                    months following the Initial Six Month
                                    Period subject to a maximum number of up to
                                    1 million shares per month during such
                                    period.

Selection of Bookrunning            For each underwritten offering in which PD
Managing Underwriter                participates, the Company will have the
                                    right to select the underwriter subject to
                                    PD's reasonable approval.

Certain Time Limitations            Under certain circumstances, the Company may
                                    postpone, once in any 360-day period, an
                                    underwritten offering for up to 30 days,
                                    subject to an appropriate board
                                    determination (e.g., a


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                                    pending material transaction).

Selling Efforts                     At PD's request, the Company will during the
                                    Initial Six Month Period enter into
                                    underwriting agreements (containing
                                    customary terms and conditions that will
                                    inure to the benefit of PD) and participate
                                    in customary selling efforts, such as road
                                    shows.

                                    SPCC will use its reasonable best efforts to
                                    provide full management support for any
                                    offering pursuant to a demand registration,
                                    including the following: SPCC will use its
                                    reasonable best efforts to arrange, organize
                                    and participate in customary "road show"
                                    presentations to institutional investors,
                                    analysts, money managers and others. Such
                                    presentations will take place in such
                                    locations, include such members of
                                    management and last for such duration as
                                    SPCC and the underwriters deem appropriate.
                                    Such presentations will be carried out in a
                                    manner comparable to similar presentations
                                    for issuances of the size and complexity
                                    involved.

Underwriting Agreement              With respect to any demand registration that
                                    will be an underwritten offering, SPCC will
                                    enter into a customary underwriting
                                    agreement with the underwriters that is
                                    reasonably satisfactory to PD and contains
                                    such terms as are customarily included in
                                    underwriting agreements, including customary
                                    indemnities no less favorable to the
                                    recipient than those contained in
                                    underwriting agreements with respect to
                                    offerings of similar size and complexity. PD
                                    will enter into such an underwriting
                                    agreement at the request of SPCC. All
                                    representations, warranties and other
                                    agreements on the part of SPCC to and for
                                    the benefit of the underwriters will also be
                                    made to and for the benefit of PD. PD will
                                    not be required to make any representations,
                                    warranties or agreements other than those
                                    regarding PD, its Registrable Securities,
                                    its intended method of distribution and that
                                    which may be required by law.

Lockups                             The Company and, to the extent so requested
                                    by the managing underwriter for an
                                    underwritten offering under the Agreement,
                                    the executive officers and directors of the
                                    Company will be subject to appropriate
                                    lockup obligations with respect to any
                                    underwritten offering, for up to 10 days
                                    prior to and 60 (or, if so requested by the
                                    managing underwriter in connection with any
                                    particular underwritten offering, up to 90)
                                    days after such offering has been effected
                                    or terminated.

                                    PD will be subject to appropriate holdback
                                    obligations with respect to any Company
                                    registration of Company stock, for up


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                                    to 10 days prior to and 60 (or, if so
                                    requested by the managing underwriter in
                                    connection with any particulars underwritten
                                    offering, up to 90) days after such offering
                                    has been effected or terminated.

Indemnification/                    The Company and PD will provide customary
Contribution                        indemnification/contribution protection to
                                    the underwriters for misstatements or
                                    omissions in connection with information
                                    supplied for inclusion in the Shelf
                                    Registration, including without limitation
                                    any prospectus supplement.

Expenses                            PD will bear those expenses directly
                                    attributable to the registration of its
                                    Registrable Securities, including
                                    registration and filing fees, fees and
                                    expenses of compliance with "Blue Sky" laws,
                                    out-of-pocket expenses and legal and
                                    accounting expenses; provided, that such
                                    expenses are reasonable and customary. In
                                    addition, PD will be responsible for its own
                                    underwriting discounts and commissions and
                                    transfer taxes attributable to its sales.
                                    Notwithstanding the foregoing, SPCC will be
                                    responsible for, and PD will not bear, any
                                    internal expenses of SPCC, including
                                    overhead and salaries and expenses of its
                                    officers and employees.

Assignability                       The registration rights granted to PD will
                                    be assignable to the indirect trust
                                    shareholders of PD and/or beneficiaries of
                                    such trusts and to transferees of greater
                                    than 50% of the original number of PD's
                                    Registrable Shares.

Third Party Registration Rights     If SPCC grants registration rights to other
                                    Third Party, such rights will be on the same
                                    terms and conditions as the rights granted
                                    to PD under the Registration Rights
                                    Agreement.

                                    In all events, SPCC will not provide
                                    registration rights to any holder or
                                    prospective holder of SPCC shares that are
                                    more favorable, in terms of timing or
                                    otherwise, than the rights conferred upon PD
                                    under the Registration Rights Agreement
                                    unless PD is also provided with the
                                    opportunity to receive such more favorable
                                    rights.


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