Exhibit 10.20

FIRST AMENDMENT TO AMENDED AND RESTATED

REVOLVING CREDIT AGREEMENT

THIS FIRST AMENDMENT TO AMENDED AND RESTATED REVOLVING CREDIT AGREEMENT (this
“Amendment”) dated effective December 13, 2006, is entered into by and among
ONEOK PARTNERS, L.P., formerly known as Northern Border Partners, L.P., a
Delaware limited partnership (the “Borrower”), the several banks and other
financial institutions and lenders from time to time party hereto (the
“Lenders”), SUNTRUST BANK, in its capacity as administrative agent for the
Lenders (the “Administrative Agent”), as issuing bank (the “Issuing Bank”) and
as swingline lender (the “Swingline Lender”), WACHOVIA BANK, NATIONAL
ASSOCIATION, as syndication agent (the “Syndication Agent”) and BANK OF
MONTREAL, BARCLAYS BANK PLC, and CITIBANK, N.A., as co-documentation agents (the
“Co-Documentation Agents”). All capitalized terms used in this Amendment and not
otherwise defined herein have the meanings ascribed to such terms in the Credit
Agreement (as defined below).

Preliminary Statement

The Borrower, the Administrative Agent, the Issuing Bank, the Swingline Lender,
the Syndication Agent, the Co-Documentation Agents, and the Lenders are parties
to that certain Amended and Restated Revolving Credit Agreement dated as of
March 30, 2006 (the “Credit Agreement”), under the terms of which such Lenders
have committed to make Revolving Loans and issue Letters of Credit in an
aggregate amount not to exceed $750,000,000.

The Borrower has requested that the Lenders amend the Credit Agreement as set
forth herein. The Lenders are agreeable to such request, upon the conditions set
forth herein.

NOW THEREFORE, in consideration of the premises and other good and valuable
consideration, the receipt and adequacy of which are hereby acknowledged by the
parties hereto, the Borrower, the Guarantor, the Administrative Agent, the
Issuing Bank, the Swingline Lender, the Syndication Agent, the Co-Documentation
Agents and the Lenders hereby agree as follows:

Section 1. Amendments to Credit Agreement

(a) Amendment to Section 1.1. Section 1.1 of the Credit Agreement is hereby
amended by replacing the definitions of “Leverage Ratio” and “Material Project
EBITDA Adjustments” in their entirety with the following definitions:

“Leverage Ratio” shall mean, as of any date, the ratio of (i) Consolidated Total
Debt as of such date (excluding an amount of Hybrid Securities not to exceed a
total of 15% of Consolidated Total Capitalization) to (ii) Adjusted Consolidated
EBITDA for the four consecutive Fiscal Quarters ending on or immediately prior
to such date.

“Material Project EBITDA Adjustments” shall mean, with respect to each Material
Project, (A) prior to completion of the Material Project, a percentage

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(based on the then-current completion percentage of the Material Project) of an
amount to be approved by the Administrative Agent as the projected Consolidated
EBITDA attributable to such Material Project for the first twelve month period
following completion (such amount to be determined based on contracts relating
to such Material Project, the creditworthiness of the other parties to such
contracts and projected revenues from such contracts, capital costs and
expenses, scheduled completion, and other factors deemed appropriate the
Administrative Agent), which may, at the Borrower’s option, be added to actual
Consolidated EBITDA for the Borrower and its Subsidiaries for the fiscal quarter
in which construction of such Material Project commences and for each fiscal
quarter thereafter until completion of the Material Project (net of any actual
Consolidated EBITDA attributable to such Material Project following its
completion), provided that if construction of the Material Project is not
completed by the scheduled completion date, then the foregoing amount shall be
reduced by the following percentage amounts depending on the period of delay for
completion (based on the period of actual delay or then-estimated delay,
whichever is longer): (i) longer than 90 days, but not more than 180 days, 25%,
(ii) longer than 180 days but not more than 270 days, 50%, and (iii) longer than
270 days, 100%; and (B) beginning with the first full fiscal quarter following
completion of the Material Project and for the two immediately succeeding fiscal
quarters, an amount to be approved by the Administrative Agent as the projected
Consolidated EBITDA attributable to the Material Project (determined in the same
manner set forth in clause (A) above) for the balance of the four full fiscal
quarter period following completion shall be added to the actual Consolidated
EBITDA attributable to the Material Project for such fiscal quarter or quarters,
for determining Consolidated EBITDA for the fiscal quarter then ending and the
immediately preceding three fiscal quarters. Notwithstanding the foregoing,
(i) no such additions shall be allowed with respect to any Material Project
unless not later than 45 days prior to commencement of construction thereof, the
Borrower shall have delivered to the Administrative Agent written pro forma
projections of Consolidated EBITDA attributable to such Material Project and
such other information and documentation as the Administrative Agent may
reasonably request, all in form and substance satisfactory to the Administrative
Agent, and (ii) the aggregate amount of all Material Project EBITDA Adjustments
during any period shall be limited to 20% of the total actual Consolidated
EBITDA of the Borrower and its Subsidiaries for such period (which total actual
Consolidated EBITDA shall be determined without including any Material Project
EBITDA Adjustments or any adjustments in respect of any Acquisitions or
Dispositions as provided in the definition of Consolidated EBITDA).

(b) Amendment to Section 1.1. Section 1.1 of the Credit Agreement is hereby
further amended by inserting the following definitions of “Consolidated
Capitalization”, “Hybrid Securities”, and “Overland Pass Agreement” in their
proper alphabetical order:

“Consolidated Total Capitalization” shall mean, without duplication, the sum of
(a) all of the shareholders’ equity or net worth of the Borrower and its

 

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Subsidiaries on a consolidated basis, as determined in accordance with GAAP plus
(b) Consolidated Total Debt.

“Hybrid Securities” means any trust preferred securities, or deferrable interest
subordinated debt with a maturity of at least 20 years, which provides for the
optional or mandatory deferral of interest or distributions, issued by the
Borrower, or any business trusts, limited liability companies, limited
partnerships or similar entities (i) substantially all of the common equity,
general partner or similar interests of which are owned (either directly or
indirectly through one or more wholly owned Subsidiaries) at all times by the
Borrower or any of its Subsidiaries, (ii) that have been formed for the purpose
of issuing such trust preferred securities or deferrable interest subordinated
debt and (iii) substantially all the assets of which consist of (A) subordinated
debt of the Borrower or a Subsidiary of the Borrower and (B) payments made from
time to time on the subordinated debt.

“Overland Pass Agreement” means that certain Amended and Restated Limited
Liability Company Agreement of Overland Pass Pipeline Company LLC dated May 31,
2006, between Williams Field Services Company, LLC, and ONEOK Overland Pass
Holdings, L.L.C., as amended.

(c) Amendment to Section 7.8. Section 7.8 of the Credit Agreement is hereby
amended by replacing such Section in its entirety with the following:

Section 7.8 Restrictive Agreements. The Borrower will not, and will not permit
any Subsidiary to, directly or indirectly, enter into, incur or permit to exist
any agreement that prohibits, restricts or imposes any condition upon (a) the
ability of the Borrower or any Subsidiary to create, incur or permit any Lien
upon any of its assets or properties, whether now owned or hereafter acquired,
to secure any obligations owing under the Loan Documents, except as provided for
(w) by the Overland Pass Agreement, (x) by the Viking Indenture, (y) so long as
Pipeline or Guardian is a Subsidiary of the Borrower, by the Pipeline Credit
Agreement or the Guardian Agreements, respectively, and (z) by indentures or
other agreements governing publicly issued Indebtedness of the Borrower
requiring that such Indebtedness be secured by an equal and ratable Lien with
any Lien that may be granted to secure any obligations owing under the Loan
Documents, or (b) the ability of any Subsidiary to pay dividends or other
distributions with respect to its Capital Stock, to make or repay loans or
advances to the Borrower or any other Subsidiary, to Guarantee Indebtedness of
the Borrower or any other Subsidiary or to transfer any of its property or
assets to the Borrower or any Subsidiary of the Borrower; provided, that (i) the
foregoing shall not apply to restrictions or conditions imposed by law or
by this Agreement or any other Loan Document or any loan or credit agreement
governing Indebtedness permitted under Section 7.1(a) or any Hybrid Securities,
(ii) the foregoing shall not apply to customary restrictions and conditions
contained in agreements relating to the sale of a Subsidiary pending such sale,
provided such restrictions and conditions apply only to the Subsidiary that is
sold and such sale is permitted hereunder, (iii) clause

 

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(a) shall not apply to restrictions or conditions imposed by any agreement
relating to secured Indebtedness permitted by this Agreement, or so long as
Guardian is a Subsidiary of the Borrower, the Guardian Agreements, in each case
so long as such restrictions and conditions apply only to the property or assets
securing such Indebtedness, and (iv) clause (a) shall not apply to customary
provisions in leases restricting the assignment thereof.

Section 2. No Obligation. Notwithstanding this Amendment, the Lenders shall have
no further obligation to extend, renew or modify the Credit Agreement as amended
by this Amendment and no further obligation of any kind in excess of those
expressly set forth herein shall be inferred from this Amendment.

Section 3. Ratification. The Borrower and the Guarantor hereby ratify each of
their respective obligations under the Credit Agreement, the Guaranty Agreement
and the Loan Documents to which they are a party, and agree and acknowledge that
the Credit Agreement, the Guaranty and each of the Loan Documents shall continue
in full force and effect as amended and modified by this Amendment. Nothing in
this Amendment extinguishes, novates or releases any right, claim or entitlement
of any of the Lenders created by or contained in any of such documents nor is
the Borrower or the Guarantor released from any covenant, warranty or obligation
created by or contained therein except as expressly provided herein. The
Guarantor has reviewed this Amendment and, as deemed necessary by the Guarantor,
received legal advice regarding its content. The Guarantor consents to the
execution of this Amendment by the Borrower. The Guarantor is executing this
Amendment below to agree and confirm that its obligations under the Guaranty
Agreement remain in full force and effect unaffected by this Amendment. The
Guarantor understands and agrees that it remains fully primarily liable for the
“Guaranteed Obligations” (as defined in the Guaranty Agreement).

Section 4. Representations True; No Default. The Borrower represents and
warrants to the Administrative Agent and the Lenders that:

(a) this Amendment has been duly authorized, executed and delivered on behalf of
the Borrower. The Credit Agreement as amended hereby and the Notes, together
with each other Loan Document to which the Borrower is a party, constitute valid
and legally binding agreements of the Borrower enforceable in accordance with
their terms;

(b) the execution, delivery and performance by the Borrower of this Amendment
(i) does not require any consent or approval of, registration or filing with, or
any action by, any Governmental Authority, except those as have been obtained or
made and are in full force and effect, (ii) will not violate any Requirements of
Law applicable to the Borrower or any of its Subsidiaries or any judgment, order
or ruling of any Governmental Authority, (iii) will not violate or result in a
default under any indenture, agreement or other instrument binding on the
Borrower or any of its Subsidiaries or any of its assets or give rise to a right
thereunder to require any payment to be made by the Borrower or any of its
Subsidiaries, in each case other than violations, defaults or rights which could
not reasonably expected to result in a Material Adverse Effect, and (iv) will
not result in the creation or imposition of any Lien on any asset of the
Borrower or any of its Subsidiaries, except Liens (if any) created under the
Loan Documents.

 

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(c) the representations and warranties of the Borrower contained in Article IV
of the Credit Agreement are true and correct in all material respects on and as
of the date hereof as though made on and as of the date hereof, except to the
extent such representations and warranties relate solely to an earlier date; and

(d) after giving effect to this Amendment, there has not occurred and is
continuing an Event of Default or any event which with notice or lapse of time
would become an Event of Default.

Section 5. Effectiveness. This Amendment shall become effective when, and only
when, the Borrower, the Guarantor and the Required Lenders shall have executed a
counterpart of this Amendment and the Administrative Agent shall have received
delivery of same. The execution, delivery and effectiveness of this Amendment
shall not, except as expressly provided herein, operate as a waiver of any
right, power or remedy of the Lenders under the Credit Agreement, nor constitute
a waiver of any provision of the Credit Agreement. This Amendment shall
constitute a Loan Document for all purposes of the Credit Agreement.

Section 6. Expenses. The Borrower agrees to pay on demand all costs and
expenses, if any (including, without limitation, reasonable counsel fees and
expenses), in connection with the negotiation, preparation and enforcement
(whether through negotiations, legal proceedings or otherwise) of this
Amendment, including, without limitation, reasonable counsel fees and expenses
in connection with the enforcement of rights under this Section.

Section 7. Miscellaneous Provisions.

(a) From and after the execution and delivery of this Amendment, the Credit
Agreement shall be deemed to be amended and modified as herein provided, but
except as so amended and modified the Credit Agreement, the Notes and all other
Loan Documents shall continue in full force and effect.

(b) The Credit Agreement and this Amendment shall be read and construed as one
and the same instrument.

(c) Any reference in any Loan Document to the Credit Agreement shall be a
reference to the Credit Agreement as amended by this Amendment.

(d) This Amendment shall be construed in accordance with and governed by the
laws of the State of New York and of the United States of America.

(e) This Amendment may be signed in any number of counterparts and by different
parties in separate counterparts, each of which shall be deemed an original but
all of which together shall constitute one and the same instrument. Delivery of
an executed counterpart of this Amendment by facsimile transmission or by
electronic mail in pdf form shall be as effective as delivery of a manually
executed counterpart hereof.

(f) The headings herein shall be accorded no significance in interpreting this
Amendment.

 

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Section 8. Binding Effect. The Amendment shall be binding upon and inure to the
benefit of the Borrower, the Administrative Agent, the Issuing Bank, the
Swingline Lender, the Co-Documentation Agents and the Lenders and the successors
and assigns of such parties. The Borrower shall not have the right to assign its
rights hereunder or any interest herein.

Section 9. Final Agreement of the Parties. This Amendment, the Notes, the Credit
Agreement and the other Loan Documents represent the final agreement between the
parties and may not be contradicted by evidence of prior, contemporaneous or
subsequent oral agreements of the parties. There are no unwritten oral
agreements between the parties.

[Signature pages follow]

 

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IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be duly
executed by their respective authorized officers as of the day and year first
above written.

 

ONEOK PARTNERS, L.P.,

By: ONEOK Partners GP, L.L.C.,

its general partner

/s/ Jerry L. Peters

Name: Jerry L. Peters

Title: Senior Vice-President, Chief Accounting

Officer and Treasurer

 

SUNTRUST BANK

as Administrative Agent, as Issuing Bank, as

Swingline Lender and as a Lender

/s/ Peter Panos

Name: Peter Panos Title: Vice President

[Signature Page to the First Amendment to Amended and Restated Revolving Credit
Agreement]

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WACHOVIA BANK, NATIONAL ASSOCIATION

as Syndication Agent and as a Lender

/s/ Shannan Townsend

Name: Shannan Townsend

Title: Director

[Signature Page to the First Amendment to Amended and Restated Revolving Credit
Agreement]

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BMO Capital Markets Financing, Inc. as a Lender

/s/ Cahal Caromody

Name: Cahal Carmody Title: Vice President

[Signature Page to the First Amendment to Amended and Restated Revolving Credit
Agreement]

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BARCLAYS BANK PLC, as a Lender

/s/ Douglas Bernegger

Name: Douglas Bernegger

Title: Director

[Signature Page to the First Amendment to Amended and Restated Revolving Credit
Agreement]

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CITIBANK, N.A., as a Lender

/s/ Todd J. Mogil

Name: Todd J. Mogil Title: Attorney-In-Fact

[Signature Page to the First Amendment to Amended and Restated Revolving Credit
Agreement]

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UBS LOAN FINANCE LLC, as a Lender

/s/ Irja R. Otsa

Name: Irja R. Otsa

Title: Associate Director

 

/s/ Christopher M. Aitkin

Name: Christopher M. Aitkin

Title: Associate Director

[Signature Page to the First Amendment to Amended and Restated Revolving Credit
Agreement]

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ROYAL BANK OF CANADA, as a Lender

/s/ David A. McCluskey

Name: David A. McCluskey Title: Authorized Signatory

[Signature Page to the First Amendment to Amended and Restated Revolving Credit
Agreement]

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THE ROYAL BANK OF SCOTLAND PLC, as a Lender

/s/ John Preece

Name: John Preece

Title: Vice President

[Signature Page to the First Amendment to Amended and Restated Revolving Credit
Agreement]

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BANK OF AMERICA, N.A., as a Lender

/s/ Gabriela Millhorn

Name: Gabriela Millhorn Title: Senior Vice President

[Signature Page to the First Amendment to Amended and Restated Revolving Credit
Agreement]

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BNP PARIBAS, as a Lender

/s/ Larry Robinson

Name: Larry Robinson

Title: Director

 

/s/ Greg Smothers

Name: Greg Smothers

Title: Vice President

[Signature Page to the First Amendment to Amended and Restated Revolving Credit
Agreement]

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COMERICA BANK, as a Lender

/s/ Matthew J. Purchase

Name: Matthew J. Purchase Title: Vice President

[Signature Page to the First Amendment to Amended and Restated Revolving Credit
Agreement]

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MIZUHO CORPORATE BANK, LTD., as a Lender

By:

 

 

Name:   Title:  

[Signature Page to the First Amendment to Amended and Restated Revolving Credit
Agreement]

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U.S. BANK NATIONAL ASSOCIATION, as a Lender

/s/ Mark E. Thompson

Name: Mark E. Thompson Title: Senior Vice President

[Signature Page to the First Amendment to Amended and Restated Revolving Credit
Agreement]

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WELLS FARGO BANK, N.A., as a Lender

/s/ Sushim Shah

Name: Sushim Shah

Title: Vice President

[Signature Page to the First Amendment to Amended and Restated Revolving Credit
Agreement]

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Acknowledged and Agreed,

this 13th day of December, 2006

 

ONEOK PARTNERS INTERMEDIATE LIMITED PARTNERSHIP,

By: ONEOK ILP GP, L.L.C., its general partner

/s/ Jerry L. Peters

Name: Jerry L. Peters Title: Senior Vice-President, Chief Accounting Officer and
Treasurer

[Signature Page to the First Amendment to Amended and Restated Revolving Credit
Agreement]