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                                                                   EXHIBIT 10.84

                                   GUARANTEE
                                   ---------

     GUARANTEE, dated as of October 6, 2000, made by AGL RESOURCES INC., a
Georgia corporation (the "Guarantor"), in favor of SUNTRUST BANK, as
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administrative agent (in such capacity, the "Administrative Agent") for the
lenders (the "Lenders") parties to the Credit Agreement, dated as of October 6,
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2000 (as amended, supplemented or otherwise modified from time to time, the
"Credit Agreement"), among AGL CAPITAL CORPORATION (the "Borrower"), the
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Lenders, Wachovia Bank, N.A., as Documentation Agent, Merrill Lynch Capital
Corporation, as Syndication Agent and SunTrust Bank, as Administrative Agent and
CAF Advance Agent.

                             W I T N E S S E T H:
                             - - - - - - - - - -


     WHEREAS, pursuant to the Credit Agreement, the Lenders have severally
agreed to make Loans to the Borrower upon the terms and subject to the
conditions set forth therein;

     WHEREAS, it is a condition precedent to the obligation of the Lenders to
make their respective Loans to the Borrower under the Credit Agreement, to the
obligation of the Swingline Lender to make its Swingline Loans to the Borrower
thereunder, to the obligation of the Issuing Lender to issue Letters of Credit
for the account of the Borrower thereunder, and to the obligation of the Lenders
to participate in the Swingline Loans and the Letters of Credit, that the
Guarantor shall have executed and delivered this Guarantee to the Administrative
Agent for the ratable benefit of the Lenders; and

     WHEREAS, Guarantor is the parent of the Borrower, and it is to the
advantage of Guarantor that the Lenders make the Loans to the Borrower, the
Swingline Lender make the Swingline Loans to the Borrower, the Issuing Lender
issue the Letters of Credit for the account of the Borrower, and the Lenders
participate in the Swingline Loans and the Letters of Credit.

     NOW, THEREFORE, in consideration of the premises and to induce the
Administrative Agent and the Lenders to enter into the Credit Agreement and to
induce the Lenders to make their respective Loans to the Borrower under the
Credit Agreement, the Swingline Lender to make the Swingline Loans to the
Borrower thereunder, the Issuing Lender to issue Letters of Credit for the
account of the Borrower thereunder, and the Lenders to participate in the
Swingline Loans and the Letters of Credit thereunder, the Guarantor hereby
agrees with the Administrative Agent, for the ratable benefit of the Lenders, as
follows:

     1.   Defined Terms. (a) Unless otherwise defined herein, terms defined in
          --------------
the Credit Agreement and used herein shall have the meanings given to them in
the Credit Agreement.

     (b)  The following terms shall have the meanings:
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                    "Lender Hedge Agreement": all Hedge Agreements entered into
                     ----------------------
               by the Borrower with any Lender (or any Affiliate of any Lender)
               in connection with the Loans.

                    "Obligations": the collective reference to the unpaid
                     -----------
               principal of and interest on the Loans and all other obligations
               and liabilities of the Borrower to the Administrative Agent and
               the Lenders (including, without limitation, interest accruing at
               the then applicable rate provided in the Credit Agreement after
               the maturity of the Loans and Reimbursement Obligations and
               interest accruing at the then applicable rate provided in the
               Credit Agreement after the filing of any petition in bankruptcy,
               or the commencement of any insolvency, reorganization or like
               proceeding, relating to the Borrower whether or not a claim for
               post-filing or post-petition interest is allowed in such
               proceeding) to the Administrative Agent or any Lender (or in the
               case of any Lender Hedge Agreement, any Affiliate of any Lender),
               whether direct or indirect, absolute or contingent, due or to
               become due, or now existing or hereafter incurred, which may
               arise pursuant to the Credit Agreement, any Letter of Credit, the
               Loans, any Lender Hedge Agreement or any other document made,
               delivered or given in connection therewith, in each case whether
               on account of principal, interest, reimbursement obligations,
               fees, indemnities, costs, expenses or otherwise (including,
               without limitation, all fees and disbursements of counsel to the
               Administrative Agent or to the Lenders that are required to be
               paid by the Borrower or the Guarantor pursuant to the terms of
               the Credit Agreement or this Guarantee or any other Loan
               Document).

     (c)  The words "hereof," "herein" and "hereunder" and words of similar
     import when used in this Guarantee shall refer to this Guarantee as a whole
     and not to any particular provision of this Guarantee, and section and
     paragraph references are to this Guarantee unless otherwise specified.

     (d)  The meanings given to terms defined herein shall be equally applicable
     to both the singular and plural forms of such terms.

     2.   Guarantee. (a) The Guarantor hereby unconditionally and irrevocably
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guarantees to the Administrative Agent, for the ratable benefit of the Lenders
and their respective successors, indorsees, transferees and assigns, the prompt
and complete payment and performance by the Borrower when due (whether at the
stated maturity, by acceleration or otherwise) of the Obligations.

     (b)  The Guarantor further agrees to pay any and all expenses (including,
     without limitation, all fees and disbursements of counsel actually
     incurred) which may be paid or incurred by the Administrative Agent or any
     Lender in enforcing, or obtaining advice of counsel in respect of, any
     rights with respect to, or collecting, any or all of the Obligations and/or
     enforcing any rights with respect to, or collecting against, the Guarantor
     under this Guarantee. This Guarantee shall remain in full force and effect
     until the Obligations are paid in full, no Letter of Credit shall be
     outstanding and the
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     Revolving Commitments are terminated, notwithstanding that from time to
     time prior thereto the Borrower may be free from any Obligations.

     (c)  No payment or payments made by the Borrower or any other Person or
     received or collected by the Administrative Agent or any Lender from the
     Borrower or any other Person by virtue of any action or proceeding or any
     set-off or appropriation or application, at any time or from time to time,
     in reduction of or in payment of the Obligations shall be deemed to modify,
     reduce, release or otherwise affect the liability of the Guarantor
     hereunder which shall, notwithstanding any such payment or payments (other
     than payments made by the Guarantor in respect of the Obligations or
     payments received or collected from the Guarantor in respect of the
     Obligations), remain liable for the Obligations until the Obligations are
     paid in full, no Letter of Credit shall be outstanding and the Revolving
     Commitments are terminated.

     (d)  The Guarantor agrees that whenever, at any time, or from time to time,
     it shall make any payment to the Administrative Agent or any Lender on
     account of its liability hereunder, it will notify the Administrative Agent
     and such Lender in writing that such payment is made under this Guarantee
     for such purpose.

     3.   Right of Set-off. Upon the occurrence of any Event of Default, the
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Administrative Agent and each Lender is hereby irrevocably authorized at any
time and from time to time (unless the Administrative Agent or such Lender, as
applicable, has agreed to the contrary) without notice to the Guarantor, any
such notice being expressly waived by the Guarantor, to set off and appropriate
and apply any and all deposits (general or special, time or demand, provisional
or final), in any currency, and any other credits, indebtedness or claims, in
any currency, in each case whether direct or indirect, absolute or contingent,
matured or unmatured, at any time held or owing by the Administrative Agent or
such Lender to or for the credit or the account of the Guarantor, or any part
thereof in such amounts as the Administrative Agent or such Lender may elect,
against or on account of the obligations and liabilities of the Guarantor to the
Administrative Agent or such Lender hereunder and claims of every nature and
description of the Administrative Agent or such Lender against the Guarantor, in
any currency, whether arising hereunder, under the Credit Agreement, any other
Loan Document or otherwise, as the Administrative Agent or such Lender may
elect, whether or not the Administrative Agent or such Lender has made any
demand for payment and although such obligations, liabilities and claims may be
contingent or unmatured. The Administrative Agent and each Lender shall notify
the Guarantor promptly of any such set-off and the application made by the
Administrative Agent or such Lender, as the case may be, of the proceeds
thereof; provided that the failure to give such notice shall not affect the
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validity of such set-off and application. The rights of the Administrative Agent
and each Lender under this paragraph are in addition to other rights and
remedies (including, without limitation, other rights of set-off) which the
Administrative Agent or such Lender may have.

     4.   No Subrogation. Notwithstanding any payment or payments made by the
          --------------
Guarantor hereunder, or any set-off or application of funds of the Guarantor by
the Administrative Agent or any Lender, the Guarantor shall not be entitled to
be subrogated to any of the rights of the Administrative Agent or any Lender
against the Borrower or against any collateral security or guarantee or right of
offset held by the Administrative Agent or any Lender for the payment of
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the Obligations, nor shall the Guarantor seek or be entitled to seek any
contribution or reimbursement from the Borrower in respect of payments made by
the Guarantor hereunder, until all amounts owing to the Administrative Agent and
the Lenders by the Borrower on account of the Obligations are paid in full, no
Letter of Credit shall be outstanding and the Revolving Commitments are
terminated. If any amount shall be paid to the Guarantor on account of such
subrogation rights at any time when all of the Obligations shall not have been
paid in full, such amount shall be held by the Guarantor in trust for the
Administrative Agent and the Lenders, segregated from other funds of the
Guarantor, and shall, forthwith upon receipt by the Guarantor, be turned over to
the Administrative Agent in the exact form received by the Guarantor (duly
indorsed by the Guarantor to the Administrative Agent, if required), to be
applied against the Obligations, whether matured or unmatured, in such order as
the Administrative Agent may determine.

     5.   Amendments, etc. with respect to the Obligations; Waiver of Rights.
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The Guarantor shall remain obligated hereunder notwithstanding that, without any
reservation of rights against the Guarantor, and without notice to or further
assent by the Guarantor, any demand for payment of any of the Obligations made
by the Administrative Agent or any Lender may be rescinded by the Administrative
Agent or such Lender, and any of the Obligations continued, and the Obligations,
or the liability of any other party upon or for any part thereof, or any
collateral security or guarantee therefor or right of offset with respect
thereto, may, from time to time, in whole or in part, be renewed, extended,
amended, modified, accelerated, compromised, waived, surrendered or released by
the Administrative Agent or any Lender, and the Credit Agreement, any other Loan
Document and any other documents executed and delivered in connection therewith
may be amended, modified, supplemented or terminated, in whole or in part, as
the Administrative Agent (or the Required Lenders, as the case may be) may deem
advisable from time to time, and any guarantee or right of offset at any time
held by the Administrative Agent or any Lender for the payment of the
Obligations may be sold, exchanged, waived, surrendered or released. Neither the
Administrative Agent nor any Lender shall have any obligation to protect,
secure, perfect or insure any Lien at any time held by it as security for the
Obligations or for this Guarantee or any property subject thereto. When making
any demand hereunder against the Guarantor, the Administrative Agent or any
Lender may, but shall be under no obligation to, make a similar demand on the
Borrower or any other guarantor, and any failure by the Administrative Agent or
any Lender to make any such demand or to collect any payments from the Borrower
or any such other guarantor or any release of the Borrower or such other
guarantor shall not relieve the Guarantor of its obligations or liabilities
hereunder, and shall not impair or affect the rights and remedies, express or
implied, or as a matter of law, of the Administrative Agent or any Lender
against the Guarantor. For the purposes hereof "demand" shall include the
commencement and continuance of any legal proceedings.

     6.   Guarantee Absolute and Unconditional. The Guarantor waives any and all
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notice of the creation, renewal, extension or accrual of any of the Obligations
and notice of or proof of reliance by the Administrative Agent or any Lender
upon this Guarantee or acceptance of this Guarantee; the Obligations, and any of
them, shall conclusively be deemed to have been created, contracted or incurred,
or renewed, extended, amended or waived, in reliance upon this Guarantee; and
all dealings between the Borrower or the Guarantor, on the one hand, and the
Administrative Agent and the Lenders, on the other, shall likewise be
conclusively presumed to have been had or consummated in reliance upon this
Guarantee. The Guarantor waives
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diligence, presentment, protest, demand for payment and notice of default or
nonpayment to or upon the Borrower or the Guarantor with respect to the
Obligations. This Guarantee shall be construed as a continuing, absolute and
unconditional guarantee of payment without regard to (a) the validity,
regularity or enforceability of the Credit Agreement or any other Loan Document,
any of the Obligations or any other collateral security therefor or guarantee or
right of offset with respect thereto at any time or from time to time held by
the Administrative Agent or any Lender, (b) any defense, set-off or counterclaim
(other than a defense of payment or performance) which may at any time be
available to or be asserted by the Borrower against the Administrative Agent or
any Lender, or (c) any other circumstance whatsoever (with or without notice to
or knowledge of the Borrower or the Guarantor) which constitutes, or might be
construed to constitute, an equitable or legal discharge of the Borrower for the
Obligations, or of the Guarantor under this Guarantee, in bankruptcy or in any
other instance. When pursuing its rights and remedies hereunder against the
Guarantor, the Administrative Agent and any Lender may, but shall be under no
obligation to, pursue such rights and remedies as it may have against the
Borrower or any other Person or against any collateral security or guarantee for
the Obligations or any right of offset with respect thereto, and any failure by
the Administrative Agent or any Lender to pursue such other rights or remedies
or to collect any payments from the Borrower or any such other Person or to
realize upon any such collateral security or guarantee or to exercise any such
right of offset, or any release of the Borrower or any such other Person or of
any such collateral security, guarantee or right of offset, shall not relieve
the Guarantor of any liability hereunder, and shall not impair or affect the
rights and remedies, whether express, implied or available as a matter of law,
of the Administrative Agent or any Lender against the Guarantor. This Guarantee
shall remain in full force and effect and be binding in accordance with and to
the extent of its terms upon the Guarantor and its successors and assigns
thereof, and shall inure to the benefit of the Administrative Agent and the
Lenders, and their respective successors, indorsees, transferees and assigns,
until all the Obligations and the obligations of the Guarantor under this
Guarantee shall have been satisfied by payment in full and the Revolving
Commitments shall be terminated, notwithstanding that from time to time during
the term of the Credit Agreement the Borrower may be free from any Obligations.

     7.   Reinstatement. This Guarantee shall continue to be effective, or be
          -------------
reinstated, as the case may be, if at any time payment, or any part thereof, of
any of the Obligations is rescinded or must otherwise be restored or returned by
the Administrative Agent or any Lender upon the insolvency, bankruptcy,
dissolution, liquidation or reorganization of the Borrower or upon or as a
result of the appointment of a receiver, intervenor or conservator of, or
trustee or similar officer for, the Borrower or any substantial part of its
property, or otherwise, all as though such payments had not been made.

     8.   Payments. The Guarantor hereby agrees that the Obligations will be
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paid to the Administrative Agent without set-off or counterclaim in U.S. Dollars
at the office of the Administrative Agent located at 303 Peachtree Street, N.E.,
Atlanta, Georgia 30308.

     9.   Authority of Administrative Agent. The Guarantor acknowledges that the
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rights and responsibilities of the Administrative Agent under this Guarantee
with respect to any action taken by the Administrative Agent or the exercise or
non-exercise by the Administrative Agent of any option, right, request, judgment
or other right or remedy provided for herein or resulting or arising out of this
Guarantee shall, as between the Administrative Agent and the Lenders, be
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governed by the Credit Agreement and by such other agreements with respect
thereto as may exist from time to time among them, but, as between the
Administrative Agent and the Guarantor, the Administrative Agent shall be
conclusively presumed to be acting as agent for the Lenders with full and valid
authority so to act or refrain from acting, and the Guarantor shall not be under
any obligation, or entitlement, to make any inquiry respecting such authority.

     10.  Notices. All notices, requests and demands to or upon the
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Administrative Agent, any Lender or the Guarantor to be effective shall be in
writing (or by telex, fax or similar electronic transfer confirmed in writing)
and shall be deemed to have been duly given or made (1) when delivered by hand
or (2) if given by mail, when deposited in the mails by certified mail, return
receipt requested, or (3) if by telex, fax or similar electronic transfer, when
sent and receipt has been confirmed, addressed as follows:

     (a)  if to the Administrative Agent or any Lender, at its address or
     transmission number for notices provided in Section 10.2 of the Credit
     Agreement; and

     (b)  if to the Guarantor, at its address or transmission number for notices
     set forth under its signature below.

     The Administrative Agent, each Lender and the Guarantor may change its
address and transmission numbers for notices by notice in the manner provided in
this Section.

     11.  Severability. Any provision of this Guarantee which is prohibited or
          ------------
unenforceable in any jurisdiction shall, as to such jurisdiction, be ineffective
to the extent of such prohibition or unenforceability without invalidating the
remaining provisions hereof, and any such prohibition or unenforceability in any
jurisdiction shall not invalidate or render unenforceable such provision in any
other jurisdiction.

     12.  Integration. This Guarantee represents the agreement of the Guarantor
          -----------
with respect to the subject matter hereof and there are no promises or
representations by the Administrative Agent or any Lender relative to the
subject matter hereof not reflected herein.

     13.  Amendments in Writing; No Waiver; Cumulative Remedies. (a) None of the
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terms or provisions of this Guarantee may be waived, amended, supplemented or
otherwise modified except by a written instrument executed by the Guarantor and
the Administrative Agent, provided that any provision of this Guarantee may be
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waived by the Administrative Agent and the Lenders in a letter or agreement
executed by the Administrative Agent or by telex or facsimile transmission from
the Administrative Agent.

     (b)  Neither the Administrative Agent nor any Lender shall by any act
     (except by a written instrument pursuant to paragraph 13(a) hereof), delay,
     indulgence, omission or otherwise be deemed to have waived any right or
     remedy hereunder or to have acquiesced in any Default or Event of Default
     or in any breach of any of the terms and conditions hereof. No failure to
     exercise, nor any delay in exercising, on the part of the Administrative
     Agent or any Lender, any right, power or privilege hereunder shall operate
     as a waiver thereof. No single or partial exercise of any right, power or
     privilege hereunder shall preclude any other or further exercise thereof or
     the exercise of any other right, power or privilege. A waiver by the
     Administrative Agent or any Lender of any
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     right or remedy hereunder on any one occasion shall not be construed as a
     bar to any right or remedy which the Administrative Agent or such Lender
     would otherwise have on any future occasion.

     (c)  The rights and remedies herein provided are cumulative, may be
     exercised singly or concurrently and are not exclusive of any other rights
     or remedies provided by law.

     14.  Section Headings. The section headings used in this Guarantee are for
          ----------------
convenience of reference only and are not to affect the construction hereof or
be taken into consideration in the interpretation hereof.

     15.  Successors and Assigns. This Guarantee shall be binding upon the
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successors and assigns of the Guarantor and shall inure to the benefit of the
Administrative Agent and the Lenders and their successors and assigns.

     16.  GOVERNING LAW. THIS GUARANTEE SHALL BE GOVERNED BY, AND CONSTRUED AND
          -------------
INTERPRETED IN ACCORDANCE WITH, THE LAW OF THE STATE OF NEW YORK.

     17.  Submission to Jurisdiction; Waivers. The Guarantor hereby irrevocably
          -----------------------------------
and unconditionally:

                    (a)  Submits for itself and its property in any legal action
     or proceeding relating to this Guarantee and the other Loan Documents to
     which it is a party, or for recognition and enforcement of any judgment in
     respect thereof, to the non-exclusive general jurisdiction of the courts of
     the State of New York, the courts of the United States of America for the
     Southern District of New York, and appellate courts from any thereof;

                    (b)  consents that any such action or proceeding may be
     brought in such courts and waives any objection that it may now or
     hereafter have to the venue of any such action or proceeding in any such
     court or that such action or proceeding was brought in an inconvenient
     court and agrees not to plead or claim the same;

                    (c)  agrees that service of process in any such action or
     proceeding may be effected by mailing a copy thereof by registered or
     certified mail (or any substantially similar form of mail), postage
     prepaid, to the Guarantor at its address referred to in Section 10(b)
     hereof or at such other address of which the Administrative Agent shall
     have been notified pursuant thereto;

                    (d)  agrees that nothing herein shall affect the right to
     effect service of process in any other manner permitted by law or shall
     limit the right to sue in any other jurisdiction; and

                    (e)  waives, to the maximum extent not prohibited by law,
     any right it may have to claim or recover in any legal action or proceeding
     referred to in this Section 17 any special, exemplary, punitive or
     consequential damages.
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     18.  WAIVER OF JURY TRIAL. THE GUARANTOR HEREBY IRREVOCABLY AND
          --------------------
UNCONDITIONALLY WAVIES TRIAL BY JURY IN ANY LEGAL ACTION OR PROCEEDING RELATING
TO THIS AGREEMENT OR ANY OTHER LOAN DOCUMENT AND FOR ANY COUNTERCLAIM THEREIN.
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     IN WITNESS WHEREOF, the undersigned has caused this Guarantee to be duly
executed and delivered by its duly authorized officer as of the day and year
first above written.

                                        AGL RESOURCES INC.


                                        By: /s/ Donald P. Weinstein
                                            ------------------------------
                                            Name: Donald P. Weinstein

                                        Address for Notices:
                                        817 West Peachtree Street, N.W.
                                        Suite 1000
                                        Atlanta, Georgia 30308
                                        Attention:  Treasurer
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                                        Telephone:  (404) 584-3589
                                        Fax:  (404) 584-3580