Document:

<PAGE>

                                                                     EXHIBIT 4.3

                          AMENDMENT TO RIGHTS AGREEMENT

         AMENDMENT TO RIGHTS AGREEMENT (this "Amendment") dated as of the 25th
day of March 2003, between Harken Energy Corporation, a Delaware corporation
(the "Company"), and American Stock Transfer and Trust Company (successor to
Mellon Investor Services LLC, a New Jersey limited liability company (formerly
known as ChaseMellon Shareholder Services L.L.C.)), as Rights Agent (the "Rights
Agent").

                                    RECITALS

         1. The Company and the Rights Agent have previously entered into that
certain Rights Agreement, dated as of April 6, 1998 (the "Agreement").

         2. Section 27 (Supplements and Amendments) of the Agreement provides,
in part, that, as long as the Rights are redeemable, the Agreement may be
supplemented or amended without the approval of any holders of Rights.

         3. The Company desires to amend the Agreement to reduce the capital and
surplus requirement of a successor Rights Agent.

                                    AGREEMENT

         Section 1. Definitions. All capitalized terms used but not defined
herein shall have the meanings given to them in the Agreement.

         Section 2. Amendment to Section 21 of the Rights Agreement. Pursuant to
         Section 27 of the Agreement (Supplements and Amendments), the
         undersigned amend Section 21 of the Agreement by deleting the fifth
         sentence of Section 21 of the Rights Agreement in its entirety and
         replacing it with the following sentence, which sentence shall read in
         its entirety as follows:

         "Any successor Rights Agent, whether appointed by the Company or by
         such a court, shall be either (a) a corporation organized and doing
         business under the laws of the United States or the laws of any state
         of the United States or the District of Columbia, in good standing, and
         having an office in the State of Texas or the State of New York, which
         is authorized under such laws to execute corporate trust or stock
         transfer powers and is subject to the supervision or examination by
         federal or state authority and which has at the time of its appointment
         as Rights Agent a combined capital and surplus of at least $10 million
         or (b) an affiliate of such corporation."

         Section 3. Governing Law. This Amendment shall be deemed to be a
contract made under the laws of the State of Delaware and for all purposes shall
be governed by and construed in accordance with the laws of such State
applicable to contracts made and to be performed entirely within such State.

<PAGE>

         Section 4. Counterparts. This Agreement may be executed in any
number of counterparts and each of such counterparts shall for all purposes be
deemed to be an original, and all such counterparts shall together constitute
but one and the same instrument.

                                    * * * * *

<PAGE>

         IN WITNESS WHEREOF, the parties hereto have caused this Amendment to
Rights Agreement to be duly executed as of the day and year first above written.

                                       HARKEN ENERGY CORPORATION

                                       By: /s/ Bruce N. Huff
                                           -------------------------------------
                                           Bruce N. Huff
                                           President and Chief Operating Officer

                                       AMERICAN STOCK TRANSFER AND TRUST
                                       COMPANY, as Rights Agent

                                       By: /s/ Joseph Wolf
                                           -------------------------------------
                                           Name: Joseph Wolf
                                                --------------------------------
                                           Title: Vice President
                                                 -------------------------------<PAGE>

                                                                     EXHIBIT 4.4

                          AMENDMENT TO RIGHTS AGREEMENT

         AMENDMENT TO RIGHTS AGREEMENT (this "Amendment") dated as of the 21st
day of April 2003, between Harken Energy Corporation, a Delaware corporation
(the "Company"), and American Stock Transfer and Trust Company (successor to
Mellon Investor Services LLC, a New Jersey limited liability company (formerly
known as ChaseMellon Shareholder Services L.L.C.)), as Rights Agent (the "Rights
Agent").

                                    RECITALS

         1. The Company and the Rights Agent have previously entered into that
certain Rights Agreement, dated as of April 6, 1998 (the "Agreement").

         2. Section 27 (Supplements and Amendments) of the Agreement provides,
in part, that, as long as the Rights are redeemable, the Agreement may be
supplemented or amended without the approval of any holders of Rights.

         3. The Company desires to amend the Agreement to reduce the capital and
surplus requirement of a successor Rights Agent.

                                    AGREEMENT

         Section 1. Definitions. All capitalized terms used but not defined
herein shall have the meanings given to them in the Agreement.

         Amended Definition. Pursuant to Section 27 of the Agreement
(Supplements and Amendments), the undersigned wish to amend Section 1(k) of the
Agreement (Certain Definitions -- Exempt Person) by deleting the existing
Section 1(k) in its entirety and replacing it with a new Section 1(k) to read as
follows:

         "(k) "Exempt Person" shall mean (i) the Company or any Subsidiary (as
such term is hereinafter defined) of the Company, in each case including,
without limitation, in its fiduciary capacity, or any employee benefit plan of
the Company or any Subsidiary of the Company, or any entity or trustee holding
Common Stock for or pursuant to the terms of any such plan or for the purpose of
funding any such plan or funding other employee benefits for employees of the
Company or of any Subsidiary of the Company, (ii) any Person who or which is or
becomes the Beneficial Owner of 15% or more of the shares of Common Stock then
outstanding as the result of such Person's Beneficial Ownership of either of (A)
the Company's 5% Convertible Notes due 2003, or (B) the Company's 5% Senior
Convertible Notes due 2003, or acquisition from the Company of the Company's
securities, including, but not limited to securities convertible into Common
Stock, and any shares of Common Stock issued by the Company to such Person upon
conversion, exchange or redemption thereof, in exchange for the Company's 5%
Convertible Notes due 2003 and/or 5% Senior Convertible Notes held by such
Person or both, unless and until such Person, while a Beneficial Owner of 15% or
more of the shares of Common Stock then outstanding, shall become the Beneficial
Owner of additional shares of Common Stock

<PAGE>

constituting 1% or more of the then outstanding shares of Common Stock other
than pursuant to such exchange, conversion or redemption, (iii) any Person who
or which is or becomes the Beneficial Owner of 15% or more of the shares of
Common Stock then outstanding as the result of such Person's acquisition from
the Company (A) of rights to subscribe for and purchase Common Stock pursuant to
an offering of such rights which is described in the Company's registration
statement to be filed with the Securities and Exchange Commission in September
2002 (the "Rights Offering"), and any shares of Common Stock issued to such
Person upon exercise of such rights and (B) of Common Stock pursuant to the
Standby Purchase Agreement to be entered into between Lyford Investments
Enterprises Ltd. and the Company (the "Standby Purchase Agreement"), unless and
until such Person, while a Beneficial Owner of 15% or more of the shares of
Common Stock then outstanding, shall become a Beneficial Owner of additional
shares of Common Stock constituting 1% or more of the then outstanding shares of
Common Stock other than pursuant to such Rights Offering or the Standby Purchase
Agreement, except that Lyford Investments Enterprises shall also be an Exempt
Person as a result of its becoming the Beneficial Owner of additional shares of
Common Stock constituting 1% or more of the then outstanding shares of Common
Stock in connection with such Person's acquisition on April , 2003, of the
Company's 5% Senior Convertible Notes due May 26, 2003, or in connection with
such Person's acquisition of Common Stock upon the redemption or conversion of
such Notes into shares of Common Stock pursuant to the terms of the such Notes;
(iv) any Person who or which is or becomes the Beneficial Owner of 15% or more
of the shares of Common Stock then outstanding as the result of such Person's
Beneficial Ownership of the Company's Series G1 Convertible Preferred Stock or
Series G2 Convertible Preferred Stock, or acquisition from the Company of the
Company's securities, including, but not limited to securities convertible into
Common Stock, and any shares of Common Stock issued by the Company to such
Person upon conversion, exchange or redemption thereof, in exchange for the
Company's Series G1 Convertible Preferred Stock or Series G2 Convertible
Preferred Stock held by such Person or both, unless and until such Person, while
a Beneficial Owner of 15% or more of the shares of Common Stock then
outstanding, shall become the Beneficial Owner of additional shares of Common
Stock constituting 1% or more of the then outstanding shares of Common Stock
other than pursuant to such exchange, conversion or redemption."

         Section 3. Governing Law. This Amendment shall be deemed to be a
contract made under the laws of the State of Delaware and for all purposes shall
be governed by and construed in accordance with the laws of such State
applicable to contracts made and to be performed entirely within such State.

         Section 4. Counterparts. This Agreement may be executed in any number
of counterparts and each of such counterparts shall for all purposes be deemed
to be an original, and all such counterparts shall together constitute but one
and the same instrument.

                                    * * * * *

<PAGE>

         IN WITNESS WHEREOF, the parties hereto have caused this Amendment to
Rights Agreement to be duly executed as of the day and year first above written.

                                       HARKEN ENERGY CORPORATION

                                       By: /s/ Anna M. Williams

                                           -------------------------------------
                                           Anna M. Williams,
                                           Executive Vice President-Finance and
                                           Chief Financial Officer

                                       AMERICAN STOCK TRANSFER AND TRUST
                                       COMPANY, as Rights Agent

                                       By: /s/ Cynthia Trotman-Inniss
                                           -------------------------------------
                                           Name:  Cynthia Trotman-Inniss
                                                  ------------------------------
                                           Title: Manager  Reorg  - V.P.
                                                  ------------------------------

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00051-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00051-of-00352.parquet"}]]