Exhibit 10.3

COMMITMENT INCREASE AND ACCESSION AGREEMENT

THIS COMMITMENT INCREASE AND ACCESSION AGREEMENT (this “Agreement”) dated as of
July 17, 2008, is among DNB NOR BANK ASA (“DnB NOR”) and MERRILL LYNCH BANK USA
(“Merrill” and, together with DnB Nor, each a “New Lender” and collectively, the
“New Lenders”); EXPORT DEVELOPMENT CANADA (“EDC”) and COMPASS BANK (“Compass”
and, together with EDC, each an “Existing Lender” and collectively, the
“Existing Lenders”); XTO ENERGY INC., a Delaware corporation (the “Borrower”);
and JPMORGAN CHASE BANK, N.A., as administrative agent (in such capacity,
together with its successors in such capacity, the “Administrative Agent”) for
the lenders party to the Credit Agreement referred to below. Each capitalized
term used herein but not otherwise defined herein has the meaning given such
term in the Credit Agreement.

R E C I T A L S

A. The Borrower, the Administrative Agent and the Lenders party thereto are
parties to that certain Amended and Restated 5-Year Revolving Credit Agreement
dated as of April 1, 2005 (as amended by the First Amendment to 5-Year Revolving
Credit Agreement dated as of March 10, 2006, the Second Amendment to 5-Year
Revolving Credit Agreement dated as of October 25, 2006, the Third Amendment to
5-Year Revolving Credit Agreement dated as of March 19, 2007, and the Fourth
Amendment to 5-Year Revolving Credit Agreement dated as of February 6, 2008, the
“Credit Agreement”), pursuant to which the Lenders have made certain loans to
and extensions of credit for the account of the Borrower.

B. The Borrower has heretofor requested pursuant to Section 2.02 of the Credit
Agreement that the aggregate amount of the Lenders’ Commitments be increased to
$2,840,000,000 by adding to the Credit Agreement the New Lenders (which for
purposes of Section 2.02 of the Credit Agreement shall constitute CI Lenders)
and by allowing the Existing Lenders, which are currently Lenders under the
Credit Agreement, to increase their respective Commitments, all as more
particularly specified herein.

C. NOW, THEREFORE, in consideration of the premises and the mutual covenants
herein contained, for good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the parties hereto agree as
follows:

Section 1. Commitment Increase.

(a) Pursuant to Section 2.02 of the Credit Agreement, effective as of the
Effective Date (used herein as defined below):

 

  (i) DnB NOR is hereby added as a Lender under the Credit Agreement with a
Commitment of $175,000,000;

 

  (ii) Merrill is hereby added as a Lender under the Credit Agreement with a
Commitment of $100,000,000;

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  (iii) EDC’s Commitment is hereby increased from $112,500,000 to $150,000,000;
and

 

  (iv) Compass’ Commitment is hereby increased from $50,000,000 to $77,500,000.

(b) Effective as of the Effective Date:

 

  (i) each New Lender shall become a Lender for all purposes of the Credit
Agreement and shall have all of the rights and obligations of a Lender
thereunder; and

 

  (ii) the amount of each New Lender’s Commitment and each Existing Lender’s
Commitment hereby supplements Schedule 2.01 to the Credit Agreement, such that
after giving effect to the Commitment Increase contemplated hereby, Schedule
2.01 of the Credit Agreement is amended and restated to read as set forth on
Schedule 2.01 attached hereto.

Section 2. Representations and Warranties; Agreements. Each New Lender and each
Existing Lender hereby: (a) represents and warrants that (i) in the case of each
New Lender, it has full power and authority, and has taken all action necessary,
to execute and deliver this Agreement and to consummate the transactions
contemplated hereby and to become a Lender under the Credit Agreement, (ii) in
the case of each New Lender, it satisfies the requirements, if any, specified in
the Credit Agreement that are required to be satisfied by it in order to become
a Lender under the Credit Agreement, (iii) from and after the Effective Date (as
defined herein), it shall be bound by the provisions of the Credit Agreement as
a Lender thereunder and shall have the obligations of a Lender thereunder to the
extent of its Commitment, (iv) it has received a copy of the Credit Agreement,
together with copies of the most recent financial statements delivered
thereunder, and such other documents and information as it has deemed
appropriate to make its own credit analysis and decision to enter into this
Agreement and to acquire or increase its Commitment, as the case may be, on the
basis of which it has made such analysis and decision independently and without
reliance on the Administrative Agent or any other Lender, and (v) if it is a New
Lender which is a Foreign Lender, attached to this Agreement is any
documentation required to be delivered by it pursuant to the terms of the Credit
Agreement, duly completed and executed by it; and (b) agrees that (i) it will,
independently and without reliance on the Administrative Agent or any other
Lender, and based on such documents and information as it shall deem appropriate
at the time, continue to make its own credit decisions in taking or not taking
action under the Credit Agreement, and (ii) it will perform in accordance with
the terms of the Credit Agreement, all of the obligations which by the terms of
the Credit Agreement are required to be performed by it as a Lender to the
extent of its Commitment (including, without limitation, any obligations of it,
if any, under Section 2.02(c) of the Credit Agreement).

Section 3. Effectiveness. This Agreement shall become effective as of July 17,
2008 (the “Effective Date”), subject to the Administrative Agent’s receipt of

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(a) counterparts of this Agreement duly executed on behalf of each New Lender,
each Existing Lender and the Borrower; and (b) an Administrative Questionnaire
duly completed by each New Lender.

Section 4. Foreign Lenders. If any New Lender is organized under the laws of a
jurisdiction outside the United States, it will provide, following the Effective
Date, the forms specified in Section 2.17(e) of the Credit Agreement, at the
times specified therein, duly completed and executed by such New Lender.

Section 5. Counterparts. This Agreement may be executed in counterparts (and by
different parties hereto on different counterparts), each of which shall
constitute an original, but all of which when taken together shall constitute a
single contract. Delivery of an executed counterpart of a signature page of this
Agreement by facsimile or other electronic image scan transmission shall be as
effective as delivery of a manually executed counterpart of this Agreement.

Section 6. Governing Law. THIS AGREEMENT SHALL BE CONSTRUED IN ACCORDANCE WITH
AND GOVERNED BY THE LAWS OF THE STATE OF TEXAS.

Section 7. Severability. In case any one or more of the provisions contained in
this Agreement should be held invalid, illegal or unenforceable in any respect,
none of the parties hereto shall be required to comply with such provision for
so long as such provision is held to be invalid, illegal or unenforceable, but
the validity, legality and enforceability of the remaining provisions contained
herein and in the Credit Agreement shall not in any way be affected or impaired.
The parties hereto shall endeavor in good-faith negotiations to replace the
invalid, illegal or unenforceable provisions with valid provisions the economic
effect of which comes as close as possible to that of the invalid, illegal or
unenforceable provisions.

Section 8. Notices. All communications and notices hereunder shall be in writing
and given as provided in Section 9.01 of the Credit Agreement. All
communications and notices hereunder to each New Lender shall be given to it at
the address set forth in its Administrative Questionnaire.

[Signature Pages Follow]

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IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be duly
executed as of the date first written above.

 

    XTO ENERGY INC.     By:   /s/ Brent W. Clum        

Brent W. Clum

Senior Vice President & Treasurer

 

[Signature Page to Commitment Increase and Accession Agreement]

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Administrative Agent:     JPMORGAN CHASE BANK, N.A.     By:   /s/ Robert W.
Traband        

Robert W. Traband

Executive Director

 

[Signature Page to Commitment Increase and Accession Agreement]

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New Lender:     DNB NOR BANK ASA     By:   /s/ Philip F. Kurpiewski        

Name: Philip F. Kurpiewski

Title: Senior Vice President

            By:   /s/ Stian Lovseth        

Name: Stian Lovseth

Title: Vice President

[Signature Page to Commitment Increase and Accession Agreement]

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New Lender:     MERRILL LYNCH BANK USA     By:   /s/ Derek Befus        

Name: Derek Befus

Title: Vice President

[Signature Page to Commitment Increase and Accession Agreement]

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Existing Lender:     EXPORT DEVELOPMENT CANADA     By:   /s/ Vivianne Bouchard  
     

Name: Vivianne Bouchard

Title: Financing Manager

            By:   /s/ Quynh Nguyen        

Name: Quynh Nguyen

Title: Senior Associate

[Signature Page to Commitment Increase and Accession Agreement]

 

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Existing Lender:     COMPASS BANK     By:   /s/ Murray Brasseux        

Name: Murray Brasseux

Title: Executive Vice President

                     

[Signature Page to Commitment Increase and Accession Agreement]

 

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SCHEDULE 2.01

COMMITMENTS

 

Lender

   Amount of
Commitment    Applicable
Percentage

JPMorgan Chase Bank, N.A.

   $188,750,000.00    6.65%

Bank of America, N.A.

   $188,750,000.00    6.65%

DnB NOR Bank ASA

   $175,000,000.00    6.16%

Export Development Canada

   $150,000,000.00    5.28%

BNP Paribas

   $145,000,000.00    5.11%

BMO Capital Markets Financing, Inc. (f/k/a Harris Nesbitt Financing, Inc.)

   $145,000,000.00    5.11%

The Bank of Tokyo-Mitsubishi UFJ, Ltd.

   $145,000,000.00    5.11%

Citibank, N.A.

   $145,000,000.00    5.11%

SunTrust Bank

   $145,000,000.00    5.11%

Wachovia Bank, National Association

   $145,000,000.00    5.11%

The Royal Bank of Scotland plc

   $145,000,000.00    5.11%

Morgan Stanley Bank

   $100,000,000.00    3.52%

Barclays Bank PLC

   $100,000,000.00    3.52%

Deutsche Bank AG New York Branch

   $100,000,000.00    3.52%

Fortis Capital Corp.

   $100,000,000.00    3.52%

Wells Fargo Bank, N.A.

   $100,000,000.00    3.52%

Schedule 2.01 to Commitment Increase and Accession Agreement – Page 1

 

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Lender

   Amount of
Commitment    Applicable
Percentage

UBS Loan Finance LLC

   $100,000,000.00    3.52%

Credit Suisse, Cayman Islands Branch

   $100,000,000.00    3.52%

Merrill Lynch Bank USA

   $100,000,000.00    3.52%

William Street Commitment Corporation

   $87,500,000.00    3.08%

Compass Bank

   $77,500,000.00    2.73%

U.S. Bank National Association

   $50,000,000.00    1.76%

Comerica Bank

   $35,000,000.00    1.23%

The Bank of New York

   $35,000,000.00    1.23%

Natixis

   $25,000,000.00    0.88%

William Street LLC

   $12,500,000.00    0.44%          

TOTAL:

   $2,840,000,000    100%

Schedule 2.01 to Commitment Increase and Accession Agreement – Page 2