UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                          -----------------------------


                               Amendment No. 4 to
                                   SCHEDULE TO


                             Tender Offer Statement
          Under Section 14(d)(1) of the Securities Exchange Act of 1934

                          -----------------------------

                       American Natural Energy Corporation
                       (Name of Subject Company (issuer))

                           Dune Energy, Inc., Offeror
    (Names of Filing Persons (identifying status as offeror, issuer or other
                                    person))

                          -----------------------------

8% Convertible Secured Debentures due September 30, 2006            N/A
             (Title of Class of Securities)               (CUSIP Number of Class
                                                               of Securities)

                          -----------------------------

                                   Copies to:

Alan Gaines, Chief Executive Officer                    Matthew S. Cohen, Esq.
         Dune Energy, Inc.                              Eaton & Van Winkle LLP
 3050 Post Oak Boulevard, Suite 695                   3 Park Avenue, 16th floor
         Houston, TX 77056                                New York, NY 10016
                                                            (212) 779-9910

           (Name, address, and telephone numbers of persons authorized
       to receive notices and communications on behalf of filing persons)

                          -----------------------------

                            Calculation of Filing Fee
- --------------------------------------------------------------------------------
    Transaction valuation*                               Amount of filing fee

         $ 4,303,750                                            $860.75
- --------------------------------------------------------------------------------
* Calculated solely for purposes of determining the filing fee. The purchase
price, as described herein, is fifty-five percent (55%) of the principal amount
outstanding under the American Natural Energy Corporation 8% Convertible Secured
Debentures due 2006 and is payable in the form of shares of the common stock,
$.001 par value, of the Company, based upon the average closing price as
reported on the American Stock Exchange over the ten trading days preceding the
third trading day immediately preceding the date the tender offer expires. At
December 26, 2006, the aggregate principal amount of the outstanding debentures
that are subject to the tender offer was $7,825,000 and the closing price of the
Company's common stock was $ 1.95 per share.

|X|   Check the box if any part of the fee is offset as provided by Rule
      0-11(a)(2) and identify the filing with which the offsetting fee was
      previously paid. Identify the previous filing by registration statement
      number, or the Form or Schedule and the date of its filing.

                  Amount Previously Paid: $860.75
                  Form or Registration No.: Schedule TO-T
                  Filing Party: Dune Energy, Inc.
                  Date Filed: December 28, 2006

|_|   Check the box if the filing relates solely to preliminary communications
      made before the commencement of a tender offer.

Check the appropriate boxes below to designate any transactions to which the
statement relates:

      |X|   third-party tender offer subject to Rule 14d-1.
      |_|   issuer tender offer subject to Rule 13e-4.
      |_|   going-private transaction subject to Rule 13e-3.
      |_|   amendment to Schedule 13D under Rule 13d-2.

Check the following box if the filing is a final amendment reporting the results
of the tender offer: |_|




The Schedule TO-T is hereby amended and supplemented by this Amendment No. 4 to
Schedule TO-T, as follows:

ITEM 4(a) Terms of the Transaction and ITEM 7(a) Source and Amount of Funds or
Other Consideration of Schedule TO-T are hereby amended and supplemented by
adding the following additional paragraphs:

      On February 1, 2007, the Company announced its acceptance for purchase of
Debentures, in the aggregate principal amount of $3,035,000 (the "Initial
Tendered Debentures"), which were validly tendered and not withdrawn as of
midnight, New York City time, January 31, 2007 (the "Initial Expiration Date").
The total consideration to be paid for the Initial Tendered Debentures is
856,026 shares of the Company's common stock, based upon a purchase price fixed
at 282 shares of its common stock per $1,000 principal amount of Debentures in
accordance with the formula set forth in the Offer to Purchase and previously
announced on January 29, 2007.

      By accepting the Initial Tendered Debentures as of the Initial Expiration
Date, the Company is deemed to have expressly waived the Minimum Tender Amount
as a condition to the tender offer.

      Pursuant to Rule 14d-11 promulgated under the Exchange Act, on February 1,
2007 the Company commenced a subsequent offering period, expiring on midnight,
New York City time, February 9, 2007 (the "Subsequent Expiration Date"), for the
purchase of any outstanding Debentures tendered prior to the Subsequent
Expiration Date. The Company's acceptance and purchase of any Debentures so
tendered is upon the same terms as set forth in the Offer to Purchase, including
the purchase price as fixed at 282 shares of the Company's common stock per
$1,000 principal amount of Debentures.

      The Company shall accept all validly tendered Debentures as they are
tendered during the subsequent offering period. No withdrawal rights shall apply
during the subsequent offering period in accordance with Rule 14d-7(a)(2).

      The full text of the Company's press release, relating to the expiration
and results of the initial offering period and the commencement of the
subsequent offering period, is filed herewith as Exhibit (a)(8) and is
incorporated herein by reference.

ITEM 8. Interest in Securities of Subject Company of Schedule TO-T is hereby
amended and supplemented by adding the following additional paragraph:

      On February 1, 2007, the Company accepted for purchase the Initial
Tendered Debentures, having an aggregate principal amount of $3,035,000. The
total consideration to be paid for the Initial Tendered Debentures is 856,026
shares of Dune's common stock, based upon a purchase price fixed at 282 shares
of Dune's common stock per $1,000 principal amount of Debentures in accordance
with the formula set forth in the Offer to Purchase. The outstanding principal
amount of the Initial Tendered Debentures is immediately convertible into the
Conversion Shares, at the conversion price of $0.15 per share; however, interest
accrued or accruing thereon is not convertible into Conversion Shares.
Conversion of all of the Initial Tendered Debentures would result in the
issuance to the Company of up to 20,233,333 Conversion Shares. If the
outstanding Debentures other than those Debentures held by the Company - either
as Company Owned Debentures or Initial Tendered Debentures - are not converted,
upon the Company's conversion of the Company Owned Debentures and the Initial
Tendered Debentures it would own approximately 43.2% of the issued and
outstanding shares of common stock of American Natural, and if debenture holders
other than the Company also convert their Debentures, approximately 32.1% of the
issued and outstanding shares of the common stock of American Natural, in each
case based upon 52,997,673 shares of Common Stock issued and outstanding as of
November 15, 2006 (exclusive of Conversion Shares), as disclosed on American
Natural's most recent quarterly filing for the nine months ended September 30,
2006 filed with the SEC on November 20, 2006.


Item 12. Exhibits.

      Item 12 of the Schedule TO-T is hereby amended by adding the following
exhibit:

      (a)   Tender Offer Materials


            (8)   Press Release of Dune Energy, Inc., dated February 1, 2007,
                  announcing the expiration and results of initial offering
                  period and the commencement of a subsequent offering period
                  under the tender offer.


                                    SIGNATURE

After due inquiry and to the best of my knowledge and belief, I certify that the
information set forth in this statement is true, complete and correct.


Dated February 1, 2007


                                                /s/ Alan Gaines
                                                --------------------------------
                                                Name: Alan Gaines
                                                Title: Chief Executive Officer


                                       6


                                 Exhibits Index

Exhibit No.          Description
- -----------          -----------


99(a)(8)             Press Release of Dune Energy, Inc., dated January 29, 2007,
                     announcing the expiration and results of initial offering
                     period and the commencement of a subsequent offering period
                     under the tender offer.