<PAGE>   1
                                                                     EXHIBIT 4-1


                           AMENDMENT TO LOAN DOCUMENTS

         THIS AMENDMENT TO LOAN DOCUMENTS (this "AMENDMENT") is made as of
_____________ ___, 2000, by and between NEW JERSEY RESOURCES CORPORATION (the
"BORROWER"), and PNC BANK, NATIONAL ASSOCIATION (successor by merger to
Midlantic Bank, National Association) (the "BANK").

                                   BACKGROUND

         A.       The Borrower and the Bank are parties to a certain Revolving
Credit Agreement and Term Loan Agreement, dated as of December 20, 1990, which
has heretofore been amended (as amended, the "LOAN AGREEMENT").

         B.       The Loan Agreement provides for certain loans to the Borrower
and, as evidence of the loans, the Borrower has delivered its Revolving Credit
Promissory Note, dated December 20, 1990 (the "NOTE") to the Bank, in original
principal amount of $20,000,000.00.

         C.       The Borrower and the Bank desire to amend the Loan Documents
as provided for in this Amendment.

         NOW, THEREFORE, in consideration of the mutual covenants herein
contained and intending to be legally bound hereby, the parties hereto agree as
follows:

         1.       Subject to the terms and conditions set forth herein, the Loan
Agreement is hereby amended as follows:

                  (a)      Section 1.1 Definitions and Interpretation,
"Termination Date" is deemed amended to substitute as the relevant date "January
31, 2002".

                  (b)      The Bank hereby waives the sixty (60) days notice
requirement of Section 3.4 (Extension of Termination Date).

         2.       Subject to the terms and conditions set forth herein, the Note
is hereby deemed amended to incorporate the amendments to the Loan Agreement as
to the term of the Note, without the necessity of replacing said Note.

         3.       Any and all references to the Loan Agreement or the Note in
either such document or in any document or agreement executed in connection
therewith (collectively the "LOAN DOCUMENTS") shall be deemed to refer to the
Loan Agreement or the Note, as appropriate, as amended by this Amendment. This
Amendment is deemed incorporated into each of the Loan Documents. Any initially
capitalized terms used in this Amendment without definition shall have the
meanings assigned to those terms in the Loan Documents. To the extent that any
term or provision of this Amendment is or may be inconsistent with any term or
provision in any Loan Document, the terms and provisions of this Amendment shall
control.

         4.       The Borrower hereby certifies that: (a) all of its
representations and warranties in the Loan Documents, as amended by this
Amendment, are, except as may otherwise be stated in this Amendment: (i) true
and correct as of the date of this Amendment, (ii) ratified and confirmed
without condition as if made anew, and (iii) incorporated into this Amendment by



<PAGE>   2

reference, (b) no Event of Default or event which, with the passage of time or
the giving of notice or both, would constitute an Event of Default, exists under
any Loan Document which will not be cured by the execution and effectiveness of
this Amendment, (c) no consent, approval, order or authorization of, or
registration or filing with, any third party is required in connection with the
execution, delivery and carrying out of this Amendment or, if required, has been
obtained, and (d) this Amendment has been duly authorized, executed and
delivered so that it constitutes the legal, valid and binding obligation of the
Borrower, enforceable in accordance with its terms. The Borrower confirms that
the Indebtedness and other obligations under the Loan Agreement and the Note
remain outstanding without defense, set off, counterclaim, discount or charge of
any kind as of the date of this Amendment.

         5.       As a condition precedent to the effectiveness of this
Amendment, the Borrower shall comply with the following terms and conditions:

                  (a)      Execution and delivery to the Bank of this Amendment.

                  (b)      Payment by the Borrower of all legal fees and
expenses incurred by the Bank in connection with this Amendment.

                  (c)      All proceedings required to be taken by the Borrower
in connection with the transactions contemplated by this Amendment shall be
satisfactory in form and substance to the Bank and its counsel, and the Bank
shall have received such counterpart originals or certified or other copies of
such documents as the Bank may reasonably request.

         6.       This Amendment may be signed in any number of counterpart
copies and by the parties to this Amendment on separate counterparts, but all
such copies shall constitute one and the same instrument. Delivery of an
executed counterpart of a signature page to this Amendment by facsimile
transmission shall be effective as delivery of a manually executed counterpart.
Any party so executing this Amendment by facsimile transmission shall promptly
deliver a manually executed counterpart, provided that any failure to do so
shall not affect the validity of the counterpart executed by facsimile
transmission.

         7.       This Amendment will be binding upon and inure to the benefit
of the Borrower and the Bank and their respective heirs, executors,
administrators, successors and assigns.

         8.       This Amendment has been delivered to and accepted by the Bank
and will be deemed to be made in the State where the Bank's office indicated in
the Loan Documents is located. This Amendment will be interpreted and the rights
and liabilities of the parties hereto determined in accordance with the laws of
the State where the Bank's office indicated in the Loan Documents is located,
excluding its conflict of laws rules.

         9.       Except as amended hereby, the terms and provisions of the Loan
Documents remain unchanged, are and shall remain in full force and effect unless
and until modified or amended in writing in accordance with their terms, and are
hereby ratified and confirmed. Except as expressly provided herein, this
Amendment shall not constitute an amendment, waiver, consent or release with
respect to any provision of any Loan Document, a waiver of any default or Event
of Default under any Loan Document, or a waiver or release of any of the Bank's
rights and remedies (all of which are hereby reserved). THE BORROWER EXPRESSLY
RATIFIES AND CONFIRMS THE WAIVER OF JURY TRIAL PROVISIONS (IF ANY) CONTAINED IN
THE LOAN DOCUMENTS.



                                      -2-
<PAGE>   3



         WITNESS the due execution of this Amendment to Loan Documents as a
document under seal as of the date first written above.

<TABLE>
<S>                                                <C>
WITNESS / ATTEST:                                  NEW JERSEY RESOURCES
                                                   CORPORATION

                                                   By:                                     (SEAL)
---------------------------------------------         -------------------------------------
                                                   Name:
                                                        -----------------------------------------
                                                   Title:
                                                         ----------------------------------------

                                                   PNC BANK, NATIONAL ASSOCIATION

                                                   By:                                     (SEAL)
---------------------------------------------         -------------------------------------
                                                            Brian M. Begg
                                                            Vice President - Energy, Metals &
                                                            Mining Group
</TABLE>



                                      -3-


<PAGE>   4
                                                                     EXHIBIT 4-2


January 31, 2000

Mr. Glenn C. Lockwood
Senior Vice President and Chief Financial Officer
New Jersey Resources Corporation
1415 Wyckoff Road
Wall, New Jersey  07719

Re:      $10,000,000 Committed Line of Credit

Dear Mr. Lockwood:

         We are pleased to inform you that PNC Bank, National Association (the
"BANK"), has approved your request for a committed line of credit (the "LOAN")
to New Jersey Resources Corporation (the "BORROWER"). We look forward to this
opportunity to help you meet the financing needs of your business. All the
details regarding your Loan are outlined in the following sections of this
letter. If these terms are satisfactory, please follow the instructions for
proceeding with your Loan provided at the end of this letter.

1.       Facility and Use of Proceeds. This is a committed revolving line of
credit under which the Borrower may request and the Bank, subject to the terms
and conditions of this letter, will make advances to the Borrower from time to
time until the Expiration Date, in an amount in the aggregate at any time
outstanding not to exceed $10,000,000 (the "LINE OF CREDIT"). The "EXPIRATION
DATE" means January 31, 2001, or such later date as may be designated by the
Bank by written notice to the Borrower. Advances under the Line of Credit will
be used for working capital or other general business purposes of the Borrower.

2.       Note. The obligation of the Borrower to repay advances under the Line
of Credit shall be evidenced by a promissory note (the "NOTE") in form and
content satisfactory to the Bank.

         This letter (the "LETTER AGREEMENT"), the Note and the other loan
documents delivered pursuant hereto will constitute the "LOAN DOCUMENTS."
Capitalized terms not defined herein shall have the meaning ascribed to them in
the Loan Documents.

3.       Interest Rate. Interest on the unpaid balance of the Line of Credit
advances will be charged at the rates, and be payable on the dates and times,
set forth in the Note evidencing the Loan.

4.       Repayment. Subject to the terms and conditions of this letter, the
Borrower may borrow, repay and reborrow under the Line of Credit until the
Expiration Date, on which date the outstanding principal balance and any accrued
but unpaid interest shall be due and payable. Interest will be due and payable
on a monthly basis, and will be computed on the basis of a year of 360 days and
paid on the actual number of days elapsed.



<PAGE>   5

Mr. Glenn C. Lockwood
Senior Vice President and Chief Financial Officer
New Jersey Resources Corporation
______________, 2000
Page 2

5.       Covenants. Unless compliance is waived in writing by the Bank or until
payment in full of the Loan and termination of the commitment for the Line of
Credit:

         (a)      The Borrower will promptly submit to the Bank such information
relating to the Borrower's affairs (including but not limited to quarterly and
annual financial statements for the Borrower and any wholly-owned subsidiary) or
any security for the Loan as the Bank may reasonably request.

         (b)      The Borrower will not make or permit any change in the nature
of its business as carried on as of the date of this Letter Agreement or in its
senior management, board of directors or equity ownership.

         (c)      The Borrower will notify the Bank in writing of the occurrence
of an Event of Default or an act or condition which, with the passage of time,
the giving of notice or both might become an Event of Default.

         (d)      The covenants and agreements of the Borrower set forth in
Section 9 (each individually, an "INCORPORATED COVENANT"; and collectively, the
"INCORPORATED COVENANTS") of that certain Revolving Credit and Term Loan
Agreement by and between the Borrower and the Bank (by its predecessor in
interest, Midlantic National Bank) and dated as of December 20, 1990, as
heretofore amended, extended or modified (the "CREDIT AGREEMENT"), shall be
incorporated herein mutatis mutandis by this reference thereto, and shall be
deemed to have been made by the Borrower in favor of, and for the benefit of,
the Bank in connection with and for the purposes of this Letter Agreement and
the Loan; provided, however, that in the case of Section 9.11 of the Credit
Agreement, the incurrence by the Borrower of the indebtedness evidenced by the
Note provided for herein is excepted therefrom. Notwithstanding the foregoing,
(a) all capitalized terms set forth in the Incorporated Covenants and defined in
the Credit Agreement, as well as other capitalized terms set forth in any such
definitions therein, shall also be deemed to be incorporated herein mutatis
mutandis and shall have the meanings given to such terms in the Credit Agreement
for the purposes hereof, and (b) to the extent any of the Incorporated
Covenants, or any incorporated definition contains any cross-reference to, or
incorporates by reference any terms of, any provision, section, schedule or
exhibit of the Credit Agreement, such cross-reference or incorporation shall be
incorporated herein mutatis mutandis for the purposes hereof. Furthermore, for
the purposes of this paragraph, in the event that any amendment, modification or
supplement to the Credit Agreement is consented to in writing by the Bank, then
any affected Incorporated Covenant shall, upon such consent becoming effective,
be deemed to be revised for the purposes of this paragraph. The Bank shall have
the right in its sole but reasonable discretion (a) to make a determination of
the existence of any violation of an Incorporated Covenant and (b) to exercise
any remedies for such violation as provided hereunder or in the Note, in each
case without regard to any action or inaction with respect to the Credit
Agreement in connection therewith. The incorporation of the Incorporated
Covenants herein in favor of the Bank shall not be affected in any way by the
termination or expiration of the Credit Agreement. In the event of a conflict
between


<PAGE>   6

Mr. Glenn C. Lockwood
Senior Vice President and Chief Financial Officer
New Jersey Resources Corporation
______________, 2000
Page 3


the express terms of this Letter Agreement or the Note and any Incorporated
Covenant, the express terms of this Letter Agreement or the Note, as applicable,
shall control.

6.       Representations and Warranties. To induce the Bank to extend the Loan
and upon the making of any advance to the Borrower under the Line of Credit, the
Borrower represents and warrants as follows:

         (a)      The Borrower's latest financial statements provided to the
Bank are true, complete and accurate in all material respects and fairly present
the financial condition, assets and liabilities, whether accrued, absolute,
contingent or otherwise, and the results of the Borrower's operations for the
period specified therein. The Borrower's financial statements have been prepared
in accordance with generally accepted accounting principles consistently applied
from period to period subject in the case of interim statements to normal
year-end adjustments. Since the date of the latest financial statements provided
to the Bank, the Borrower has not suffered any damage, destruction or loss which
has materially adversely affected its business, assets, operations, financial
condition or results of operations.

         (b)      There are no actions, suits, proceedings or governmental
investigations pending or, to the knowledge of the Borrower, threatened against
the Borrower which could result in a material adverse change in its business,
assets, operations, financial condition or results of operations and there is no
basis known to the Borrower or its officers, directors or shareholders for any
such action, suit, proceedings or investigation.

         (c)      The Borrower has filed all returns and reports that are
required to be filed by it in connection with any federal, state or local tax,
duty or charge levied, assessed or imposed upon the Borrower or its property,
including unemployment, social security and similar taxes and all of such taxes
have been either paid or adequate reserve or other provision has been made
therefor.

         (d)      The Borrower is duly organized, validly existing and in good
standing under the laws of the state of its incorporation or organization and
has the power and authority to own and operate its assets and to conduct its
business as now or proposed to be carried on, and is duly qualified, licensed
and in good standing to do business in all jurisdictions where its ownership of
property or the nature of its business requires such qualification or licensing.

         (e)      The Borrower has full power and authority to enter into the
transactions provided for in this Letter Agreement and has been duly authorized
to do so by all necessary and appropriate action and when executed and delivered
by the Borrower, this Letter Agreement and the other Loan Documents will
constitute the legal, valid and binding obligations of the Borrower, enforceable
in accordance with their terms.

         (f)      There does not exist any default or violation by the Borrower
of or under any of the terms, conditions or obligations of: (i) its
organizational documents; (ii) any indenture, mortgage, deed of trust,
franchise, permit, contract, agreement, or other instrument to which it is a
party or


<PAGE>   7

Mr. Glenn C. Lockwood
Senior Vice President and Chief Financial Officer
New Jersey Resources Corporation
______________, 2000
Page 4


by which it is bound; or (iii) any law, regulation, ruling, order, injunction,
decree, condition or other requirement applicable to or imposed upon the
Borrower by any law or by any governmental authority, court or agency.

         (g)      The Borrower has reviewed the areas within its business and
operations which could be adversely affected by, and has developed or is
developing a program to address on a timely basis the risk that certain computer
applications used by the Borrower may be unable to recognize and perform
properly date-sensitive functions involving dates prior to and after December
31, 1999 (the "Year 2000 Problem"). The Year 2000 Problem will not result, and
is not reasonably expected to result, in any material adverse effect on the
business, properties, assets, financial condition, results of operations or
prospects of the Borrower, or the ability of the Borrower to duly and punctually
pay or perform its obligations hereunder and under the other Loan Documents.

7.       Fees. Beginning on the last day of the quarter after the date of the
Note and continuing on the last day of each quarter thereafter until the
Expiration Date, the Borrower shall pay a commitment fee to the Bank, in
arrears, at the rate of .125 percent (.125%) per annum on the average daily
balance of the Line of Credit which is undisbursed and uncancelled during the
preceding quarter. The commitment fee shall be computed on the basis of a year
of 360 days and paid on the actual number of days elapsed.

8.       Expenses. The Borrower shall reimburse the Bank for the Bank's expenses
(including the reasonable fees and expenses of the Bank's outside and in-house
counsel) in documenting and closing this transaction, in connection with any
amendments, modifications or renewals of the Loan, and in connection with the
collection of all of the Borrower's obligations to the Bank, including but not
limited to enforcement actions relating to the Loan.

9.       Events of Default. The Loan will be cross-defaulted with all other
present and future obligations of the Borrower to the Bank. Therefore, in
addition to those Events of Default set forth in the Note, and without
limitation thereof, the term "EVENT OF DEFAULT" as used herein and in the Note
and the other Loan Documents, shall include within its meaning the occurrence of
any "Event of Default" as such term is defined in the Credit Agreement.

10.      Additional Provisions. Before the first advance under the Loan, the
Borrower shall execute and deliver to the Bank the Note and other required Loan
Documents and such other instruments and documents as the Bank may reasonably
request, such as certified resolutions, incumbency certificates or other
evidence of authority. The Bank will not be obligated to make any advance under
the Line of Credit if any Event of Default or event which with the passage of
time, provision of notice or both would constitute an Event of Default shall
have occurred and be continuing.

         Prior to execution of the final Loan Documents, the Bank may terminate
this Letter Agreement if a material adverse change occurs with respect to the
Borrower, any guarantor, any collateral for the Loan or any other person or
entity connected in any way with the Loan, or if the


<PAGE>   8

Mr. Glenn C. Lockwood
Senior Vice President and Chief Financial Officer
New Jersey Resources Corporation
______________, 2000
Page 5


Borrower fails to comply with any of the terms and conditions of this Letter
Agreement, or if the Bank reasonably determines that any of the conditions
cannot be met.

         This Letter Agreement is governed by the laws of the State of New
Jersey. No modification, amendment or waiver of any of the terms of this Letter
Agreement, nor any consent to any departure by the Borrower therefrom, will be
effective unless made in a writing signed by the party to be charged, and then
such waiver or consent shall be effective only in the specific instance and for
the purpose for which given. When accepted, this Letter Agreement and the other
Loan Documents will constitute the entire agreement between the Bank and the
Borrower concerning the Loan, and shall replace all prior understandings,
statements, negotiations and written materials relating to the Loan.

         THE BORROWER AND THE BANK IRREVOCABLY WAIVE ANY AND ALL RIGHTS THEY MAY
HAVE TO A TRIAL BY JURY IN ANY ACTION, PROCEEDING OR CLAIM OF ANY NATURE ARISING
OUT OF THIS LETTER AGREEMENT AND THE TRANSACTIONS CONTEMPLATED HEREBY AND
ACKNOWLEDGE THAT THE FOREGOING WAIVER IS KNOWING AND VOLUNTARY.

         If and when a loan closing occurs, this Letter Agreement (as the same
may be amended from time to time) shall survive the closing and will serve as
our loan agreement throughout the term of the Loan.

         To accept these terms, please sign the enclosed copy of this Letter
Agreement as set forth below and the Loan Documents and return them to the Bank
within ten (10) days from the date of this Letter Agreement, or this Letter
Agreement may be terminated at the Bank's option without liability or further
obligation of the Bank.

         Thank you for giving PNC Bank this opportunity to work with your
business. We look forward to other ways in which we may be of service to your
business or to you personally.

                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]


<PAGE>   9

Mr. Glenn C. Lockwood
Senior Vice President and Chief Financial Officer
New Jersey Resources Corporation
______________, 2000
Page 6


Very truly yours,

PNC BANK, NATIONAL ASSOCIATION

By:
   --------------------------------
         Brian M. Begg
         Vice President - Energy,
         Metals & Mining Group

                                   ACCEPTANCE

With the intent to be legally bound hereby, the above terms and conditions are
hereby agreed to and accepted as of this ________ day of ___________________,
2000.

                                BORROWER:

                                NEW JERSEY RESOURCES CORPORATION

                                By:                            (SEAL)
                                   ----------------------------
                                Print Name:
                                           --------------------------
                                Title:
                                      -------------------------------