<PAGE>   1
                                                                    EXHIBIT 4.13








                           REGIONS GUARANTEE AGREEMENT

                                     BETWEEN

                         REGIONS FINANCIAL CORPORATION,
                                  AS GUARANTOR,

                                       AND

                             BANKERS TRUST COMPANY,
                              as Guarantee Trustee

                         REGIONS FINANCING TRUST [I/II]

                        DATED AS OF _______________, 2001



<PAGE>   2



                         REGIONS FINANCING TRUST [I/II]

            Certain Sections of this Guarantee Agreement relating to
                         Sections 310 through 318 of the
                          Trust Indenture Act of 1939:

<TABLE>
<CAPTION>
Section of
Trust Indenture                                                    Section of
Act Agreement                                                      Guarantee
-------------                                                      ---------
<S>      <C>                                                  <C>

310      (a)..........................................................4.1(a)

         (b).....................................................4.1(c), 2.8

         (c)....................................................Inapplicable

311      (a)..........................................................2.2(b)

         (b)..........................................................2.2(b)

         (c)....................................................Inapplicable

312      (a)..........................................................2.2(a)

         (b)..........................................................2.2(b)

313      ................................................................2.3

314      (a).............................................................2.4

         (b)....................................................Inapplicable

         (c).............................................................2.5

         (d)....................................................Inapplicable

         (e)...................................................1.1, 2.5, 3.2

         (f)........................................................2.1, 3.2

315      (a)..........................................................3.1(d)

         (b).............................................................2.7

         (c).............................................................3.1
</TABLE>


                                       -i-
<PAGE>   3

<TABLE>
<S>      <C>                                                   <C>
         (d).......................................................... .1(d)

316      (a)...................................................1.1, 2.6, 5.4

         (b).............................................................5.3

         (c).............................................................8.2

317      (a)....................................................Inapplicable

         (b)....................................................Inapplicable

318      (a)..........................................................2.1(b)

         (b).............................................................2.1

         (c)..........................................................2.1(a)
</TABLE>

Note: This reconciliation and tie sheet shall not, for any purpose, be deemed to
be a part of the Guarantee Agreement.


                                      -ii-


<PAGE>   4

                               TABLE OF CONTENTS

<TABLE>
<S>     <C>                                                                                       <C>
ARTICLE 1.  INTERPRETATION AND DEFINITIONS.........................................................1
   SECTION 1.1. Interpretation.....................................................................1
   SECTION 1.2. Definitions........................................................................2
ARTICLE 2.  TRUST INDENTURE ACT....................................................................4
   SECTION 2.1. Trust Indenture Act; Application...................................................4
   SECTION 2.2. List of Holders....................................................................5
   SECTION 2.3. Reports by the Guarantee Trustee...................................................5
   SECTION 2.4. Periodic Reports to the Guarantee Trustee..........................................5
   SECTION 2.5. Evidence of Compliance with Conditions Precedent...................................5
   SECTION 2.6. Events of Default; Waiver..........................................................6
   SECTION 2.7. Event of Default; Notice...........................................................6
   SECTION 2.8. Conflicting Interests..............................................................6
ARTICLE 3.  POWERS, DUTIES AND RIGHTS OF THE GUARANTEE TRUSTEE.....................................7
   SECTION 3.1. Powers and Duties of the Guarantee Trustee.........................................7
   SECTION 3.2. Certain Rights of Guarantee Trustee................................................8
   SECTION 3.3. Indemnity.........................................................................10
ARTICLE 4.  GUARANTEE TRUSTEE.....................................................................10
   SECTION 4.1. Guarantee Trustee: Eligibility....................................................10
   SECTION 4.2. Appointment, Removal and Resignation of the Guarantee Trustee.....................11
ARTICLE 5.  GUARANTEE.............................................................................11
   SECTION 5.1. Guarantee.........................................................................11
   SECTION 5.2. Waiver of Notice and Demand.......................................................12
   SECTION 5.3. Obligations Not Affected..........................................................12
   SECTION 5.4. Rights of Holders.................................................................13
   SECTION 5.5. Guarantee of Payment..............................................................13
   SECTION 5.6. Subrogation.......................................................................13
   SECTION 5.7. Independent Obligations...........................................................13
ARTICLE 6.  SUBORDINATION.........................................................................14
   SECTION 6.1. Subordination.....................................................................14
   SECTION 6.2. Pari Passu Guarantees.............................................................14
ARTICLE 7.  TERMINATION...........................................................................14
   SECTION 7.1. Termination.......................................................................14
ARTICLE 8.  MISCELLANEOUS.........................................................................15
   SECTION 8.1. Successors and Assigns............................................................15
   SECTION 8.2. Amendments........................................................................15
   SECTION 8.3. Notices...........................................................................15
   SECTION 8.4. Benefit...........................................................................16
   SECTION 8.5. Governing Law.....................................................................16
   SECTION 8.6. Counterparts......................................................................16
</TABLE>


                                       -i-


<PAGE>   5

         GUARANTEE AGREEMENT, dated as of _______________, 2001, executed and
delivered by REGIONS FINANCIAL CORPORATION, a Delaware corporation (the
"Guarantor") having its principal office at 417 North 20th Street, Birmingham,
Alabama 35203, and BANKERS TRUST COMPANY, a banking corporation organized under
the laws of the State of New York, as trustee (the "Guarantee Trustee"), for the
benefit of the Holders (as defined herein) from time to time of the Preferred
Securities (as defined herein) of Regions Financing Trust [I/II], a Delaware
business trust (the "Issuer").

                              W I T N E S S E T H :


         WHEREAS, pursuant to an Amended and Restated Declaration of Trust,
dated as of _______________, 2001 (the "Declaration"), among the Guarantor, as
Depositor, the Property Trustee (as defined below), the Delaware Trustee (as
defined in the Declaration) and the Administrative Trustees named therein and
the Holders from time to time of undivided beneficial interests in the assets of
the Issuer, the Issuer is issuing $_____________ aggregate Liquidation Amount
(as defined in the Declaration) of its ________% Preferred Securities,
Liquidation Amount $ ________ per capital security) (the "Preferred Securities")
representing preferred undivided beneficial interests in the assets of the
Issuer and having the terms set forth in the Declaration;


         WHEREAS, the Preferred Securities will be issued by the Issuer and the
proceeds thereof, together with the proceeds from the issuance of the Issuer's
Common Securities (as defined below), will be used to purchase the Debentures
(as defined in the Declaration) of the Guarantor which will be deposited with
Bankers Trust Company, as Property Trustee under the Declaration (the "Property
Trustee"), as trust assets; and

         WHEREAS, as incentive for the Holders to purchase Preferred Securities,
the Guarantor desires irrevocably and unconditionally to agree, to the extent
set forth herein, to pay to the Holders of the Preferred Securities the
Guarantee Payments (as defined herein) and to make certain other payments on the
terms and conditions set forth herein.

         NOW, THEREFORE, in consideration of the purchase by each Holder of
Preferred Securities, which purchase the Guarantor hereby agrees shall benefit
the Guarantor, the Guarantor executes and delivers this Guarantee Agreement to
provide as follows for the benefit of the Holders from time to time of the
Preferred Securities:

                    ARTICLE 1. INTERPRETATION AND DEFINITIONS


         SECTION 1.1.  INTERPRETATION.

         In this Guarantee Agreement, unless the context otherwise requires:


<PAGE>   6

         (a)      capitalized terms used in this Guarantee Agreement but not
defined in the preamble hereto have the respective meanings assigned to them in
Section 1.2;

         (b)      a term defined anywhere in this Guarantee Agreement has the
same meaning throughout;

         (c)      all references to "the Guarantee Agreement" or "this Guarantee
Agreement" are to this Guarantee Agreement as modified, supplemented or amended
from time to time;

         (d)      all references in this Guarantee Agreement to Articles and
Sections are to Articles and Sections of this Guarantee Agreement unless
otherwise specified;

         (e)      a term defined in the Trust Indenture Act has the same meaning
when used in this Guarantee Agreement unless otherwise defined in this Guarantee
Agreement or unless the context otherwise requires;

         (f)      a reference to the singular includes the plural and
vice-versa; and

         (g)      the masculine, feminine or neuter genders used herein shall
include the masculine, feminine and neuter genders.


         SECTION 1.2.      DEFINITIONS.

         As used in this Guarantee Agreement, the terms set forth below shall,
unless the context otherwise requires, have the following meanings:

         "AFFILIATE" of any specified Person means any other Person directly or
indirectly controlling or controlled by or under direct or indirect common
control with such specified Person; provided, however, that the Issuer shall not
be deemed to be an Affiliate of the Guarantor. For the purposes of this
definition, "control" when used with respect to any specified Person means the
power to direct the management and policies of such Person, directly or
indirectly, whether through the ownership of voting securities, by contract or
otherwise; and the terms "controlling" and "controlled" have meanings
correlative to the foregoing.

         "BOARD OF DIRECTORS" means either the board of directors of the
Guarantor or any executive or other committee duly authorized by the board of
directors of the Guarantor to act hereunder.

         "COMMON SECURITIES" means the securities representing common undivided
beneficial interests in the assets of the Issuer.

         "EVENT OF DEFAULT" means a default by the Guarantor on any of its
payment or other obligations under this Guarantee Agreement; provided, however,
that, except with


                                      -2-
<PAGE>   7

respect to a default in payment of any Guarantee Payments, the Guarantor shall
have received written notice of default and shall not have cured such default
within 60 days after receipt of such notice.


         "GUARANTEE PAYMENTS" means the following payments or distributions,
without duplication, with respect to the Preferred Securities, to the extent not
paid or made by or on behalf of the Issuer: (i) any accumulated and unpaid
Distributions (as defined in the Declaration) required to be paid on the
Preferred Securities, to the extent the Issuer shall have funds on hand
available therefor at such time, (ii) the redemption price, including all
accumulated and unpaid Distributions to the date of redemption (the "Redemption
Price"), with respect to any Preferred Securities called for redemption by the
Issuer, to the extent the Issuer shall have funds on hand available therefor at
such time, and (iii) upon a voluntary or involuntary termination, winding up or
liquidation of the Issuer, unless Debentures are distributed to the Holders, the
lesser of (a) the aggregate of the Liquidation Amount of $_____ per Preferred
Security plus accumulated and unpaid Distributions on the Preferred Securities
to the date of payment to the extent that the Issuer shall have funds available
therefor at such time and (b) the amount of assets of the Issuer remaining
available for distribution to Holders in liquidation of the Issuer (in either
case, the "Liquidation Distribution").


         "GUARANTEE TRUSTEE" means Bankers Trust Company, until a Successor
Guarantee Trustee has been appointed and has accepted such appointment pursuant
to the terms of this Guarantee Agreement, and thereafter means each such
Successor Guarantee Trustee.

         "HOLDER" means any holder, as registered on the books and records of
the Issuer, of any Preferred Securities; provided, however, that in determining
whether the holders of the requisite percentage of Preferred Securities have
given any request, notice, consent or waiver hereunder, "HOLDER" shall not
include the Guarantor, the Guarantee Trustee, or any Affiliate of the Guarantor
or the Guarantee Trustee.

         "INDENTURE" means the [Indenture] dated as of ____________________,
2001, as supplemented and amended between the Guarantor and Bankers Trust
Company, as trustee.

         "LIST OF HOLDERS" has the meaning specified in Section 2.2(a).

         "MAJORITY IN LIQUIDATION AMOUNT OF THE PREFERRED SECURITIES" means,
except as provided by the Trust Indenture Act, a vote by the Holder(s), voting
separately as a class, of more than 50% of the Liquidation Amount of all then
outstanding Preferred Securities issued by the Issuer.

         "OFFICERS' CERTIFICATE" means, with respect to any Person, a
certificate signed by the President or a Vice President of such Person, and by
the Treasurer, an Assistant Treasurer, the Secretary or an Assistant Secretary
of such Person, and delivered to the Guarantee Trustee. Any Officers'
Certificate delivered with respect to compliance with a


                                      -3-
<PAGE>   8

condition or covenant provided for in this Guarantee Agreement shall include:

         (a)      a statement that each officer signing the Officers'
Certificate has read the covenant or condition and the definitions relating
thereto;

         (b)      a brief statement of the nature and scope of the examination
or investigation undertaken by each officer in rendering the Officers'
Certificate;

         (c)      a statement that each officer has made such examination or
investigation as, in such officer's opinion, is necessary to enable such officer
to express an informed opinion as to whether or not such covenant or condition
has been complied with; and

         (d)      a statement as to whether, in the opinion of each officer,
such condition or covenant has been complied with.

         "PERSON" means a legal person, including any individual, corporation,
estate, partnership, joint venture, association, joint stock company, limited
liability company, trust, unincorporated association, or government or any
agency or political subdivision thereof, or any other entity of whatever nature.

         "RESPONSIBLE OFFICER" means, with respect to the Guarantee Trustee, any
Vice President, any Assistant Vice President, the Secretary, any Assistant
Secretary, any Assistant Treasurer, any Trust Officer or Assistant Trust Officer
or any other officer of the Corporate Trust Department of the Guarantee Trustee
and also means, with respect to a particular corporate trust matter, any other
officer to whom such matter is referred because of that officer's knowledge of
and familiarity with the particular subject.

         "SENIOR DEBT" has the meaning set forth in the Indenture.

         "SUCCESSOR GUARANTEE TRUSTEE" means a successor Guarantee Trustee
possessing the qualifications to act as Guarantee Trustee under Section 4.1.

         "TRUST INDENTURE ACT" means the Trust Indenture Act of 1939, as
amended.

         Capitalized or otherwise defined terms used but not otherwise defined
herein shall have the meanings assigned to such terms in the Declaration as in
effect on the date hereof.

                         ARTICLE 2. TRUST INDENTURE ACT


         SECTION 2.1.      TRUST INDENTURE ACT; APPLICATION.

         (a)      This Guarantee Agreement is subject to the provisions of the
Trust Indenture Act that are or would be required to be part of this Guarantee
Agreement and shall, to the extent applicable, be governed by such provisions.


                                      -4-
<PAGE>   9

         (b)      If and to the extent that any provision of this Guarantee
Agreement limits, qualifies or conflicts with the duties imposed by Sections 310
to 317, inclusive, of the Trust Indenture Act, such imposed duties shall
control.


         SECTION 2.2.      LIST OF HOLDERS.

         (a)      The Guarantor shall furnish or cause to be furnished to the
Guarantee Trustee (a) semi-annually, on or before June 1 and December 1 of each
year, a list, in such form as the Guarantee Trustee may reasonably require, of
the names and addresses of the Holders (the "List of Holders") as of a date not
more than 15 days prior to the delivery thereof, and (b) at such other times as
the Guarantee Trustee may request in writing, within 30 days after the receipt
by the Guarantor of any such request, a List of Holders as of a date not more
than 15 days prior to the time such list is furnished, in each case to the
extent such information is in the possession or control of the Guarantor and is
not identical to a previously supplied list of Holders or has not otherwise been
received by the Guarantee Trustee in its capacity as such. The Guarantee Trustee
may destroy any List of Holders previously given to it on receipt of a new List
of Holders.

         (b)      The Guarantee Trustee shall comply with its obligations under
Section 311(a), Section 311(b) and Section 312(b) of the Trust Indenture Act.


         SECTION 2.3.      REPORTS BY THE GUARANTEE TRUSTEE.

         Not later than ____________ of each year, commencing _________________,
200__, the Guarantee Trustee shall provide to the Holders such reports as are
required by Section 313 of the Trust Indenture Act, if any, in the form and in
the manner provided by Section 313 of the Trust Indenture Act. The Guarantee
Trustee shall also comply with the requirements of Section 313(d) of the Trust
Indenture Act.


         SECTION 2.4.      PERIODIC REPORTS TO THE GUARANTEE TRUSTEE.

         The Guarantor shall provide to the Guarantee Trustee, the Securities
and Exchange Commission and the Holders such documents, reports and information,
if any, as required by Section 314 of the Trust Indenture Act and the compliance
certificate required by Section 314 of the Trust Indenture Act, in the form, in
the manner and at the times required by Section 314 of the Trust Indenture Act.


         SECTION 2.5.      EVIDENCE OF COMPLIANCE WITH CONDITIONS PRECEDENT.

         The Guarantor shall provide to the Guarantee Trustee such evidence of
compliance with such conditions precedent, if any, provided for in this
Guarantee


                                      -5-
<PAGE>   10

Agreement that relate to any of the matters set forth in Section 314(c) of the
Trust Indenture Act. Any certificate or opinion required to be given by an
officer pursuant to Section 314(c)(1) may be given in the form of an Officers'
Certificate.


         SECTION 2.6.      EVENTS OF DEFAULT; WAIVER.

         The Holders of a Majority in Liquidation Amount of the Preferred
Securities may, by vote, on behalf of the Holders of all Preferred Securities,
waive any past default or Event of Default and its consequences. Upon such
waiver, any such default or Event of Default shall cease to exist, and any
default or Event of Default arising therefrom shall be deemed to have been
cured, for every purpose of this Guarantee Agreement, but no such waiver shall
extend to any subsequent or other default or Event of Default or impair any
right consequent therefrom.


         SECTION 2.7.      EVENT OF DEFAULT; NOTICE.

         (a)      The Guarantee Trustee shall, within 90 days after the
occurrence of an Event of Default, transmit by mail, first class postage
prepaid, to the Holders of all Preferred Securities, notices of all Events of
Default actually known to a Responsible Officer of the Guarantee Trustee, unless
such Events of Default have been cured before the giving of such notice,
provided, that, except in the case of a default in the payment of a Guarantee
Payment, the Guarantee Trustee shall be protected in withholding such notice if
and so long as the Board of Directors and/or Responsible Officers of the
Guarantee Trustee in good faith determines that the withholding of such notice
is in the interests of the Holders.

         (b)      The Guarantee Trustee shall not be deemed to have knowledge of
any Event of Default unless the Guarantee Trustee shall have received written
notice, or a Responsible Officer charged with the administration of this
Guarantee Agreement shall have obtained written notice, of such Event of
Default.


         SECTION 2.8.      CONFLICTING INTERESTS.

         The Declaration shall be deemed to be specifically described in this
Guarantee Agreement for the purposes of clause (i) of the first proviso
contained in Section 310(b) of the Trust Indenture Act.


                                      -6-
<PAGE>   11

          ARTICLE 3. POWERS, DUTIES AND RIGHTS OF THE GUARANTEE TRUSTEE


         SECTION 3.1.      POWERS AND DUTIES OF THE GUARANTEE TRUSTEE.

         (a)      This Guarantee Agreement shall be held by the Guarantee
Trustee for the benefit of the Holders, and the Guarantee Trustee shall not
transfer this Guarantee Agreement to any Person except a Holder exercising his
or her rights pursuant to Section 5.4(iv) or to a Successor Guarantee Trustee on
acceptance by such Successor Guarantee Trustee of its appointment to act as
Successor Guarantee Trustee. The right, title and interest of the Guarantee
Trustee shall automatically vest in any Successor Guarantee Trustee, upon
acceptance by such Successor Guarantee Trustee of its appointment hereunder, and
such vesting and cessation of title shall be effective whether or not
conveyancing documents have been executed and delivered pursuant to the
appointment of such Successor Guarantee Trustee.

         (b)      If an Event of Default has occurred and is continuing, the
Guarantee Trustee shall enforce this Guarantee Agreement for the benefit of the
Holders.

         (c)      The Guarantee Trustee, before the occurrence of any Event of
Default and after the curing of all Events of Default that may have occurred,
shall undertake to perform only such duties as are specifically set forth in
this Guarantee Agreement, and no implied covenants shall be read into this
Guarantee Agreement against the Guarantee Trustee. In case an Event of Default
has occurred (that has not been cured or waived pursuant to Section 2.6), the
Guarantee Trustee shall exercise such of the rights and powers vested in it by
this Guarantee Agreement, and use the same degree of care and skill in its
exercise thereof, as a prudent person would exercise or use under the
circumstances in the conduct of his or her own affairs.

         (d)      No provision of this Guarantee Agreement shall be construed to
relieve the Guarantee Trustee from liability for its own negligent action, its
own negligent failure to act or its own willful misconduct, except that:

                  (i)      prior to the occurrence of any Event of Default and
         after the curing or waiving of all such Events of Default that may have
         occurred:

                           (A)      the duties and obligations of the Guarantee
                  Trustee shall be determined solely by the express provisions
                  of this Guarantee Agreement, and the Guarantee Trustee shall
                  not be liable except for the performance of such duties and
                  obligations as are specifically set forth in this Guarantee
                  Agreement; and

                           (B)      in the absence of bad faith on the part of
                  the Guarantee Trustee, the Guarantee Trustee may conclusively
                  rely, as to the truth of the statements and the correctness of
                  the opinions expressed therein, upon any


                                      -7-
<PAGE>   12

                  certificates or opinions furnished to the Guarantee Trustee
                  and conforming to the requirements of this Guarantee
                  Agreement; but in the case of any such certificates or
                  opinions that by any provision hereof or of the Trust
                  Indenture Act are specifically required to be furnished to the
                  Guarantee Trustee, the Guarantee Trustee shall be under a duty
                  to examine the same to determine whether or not they conform
                  to the requirements of this Guarantee Agreement;

                  (ii)     the Guarantee Trustee shall not be liable for any
         error of judgment made in good faith by a Responsible Officer of the
         Guarantee Trustee, unless it shall be proved that the Guarantee Trustee
         was negligent in ascertaining the pertinent facts upon which such
         judgment was made;

                  (iii)    the Guarantee Trustee shall not be liable with
         respect to any action taken or omitted to be taken by it in good faith
         in accordance with the direction of the Holders of not less than a
         Majority in Liquidation Amount of the Preferred Securities relating to
         the time, method and place of conducting any proceeding for any remedy
         available to the Guarantee Trustee, or exercising any trust or power
         conferred upon the Guarantee Trustee under this Guarantee Agreement;
         and

                  (iv)     subject to Section 3.1(b), no provision of this
         Guarantee Agreement shall require the Guarantee Trustee to expend or
         risk its own funds or otherwise incur personal financial liability in
         the performance of any of its duties or in the exercise of any of its
         rights or powers, if the Guarantee Trustee shall have reasonable
         grounds for believing that the repayment of such funds or liability is
         not reasonably assured to it under the terms of this Guarantee
         Agreement or adequate indemnity against such risk or liability is not
         reasonably assured to it.


         SECTION 3.2.      CERTAIN RIGHTS OF GUARANTEE TRUSTEE.

         (a)      Subject to the provisions of Section 3.1:

                  (i)      The Guarantee Trustee may conclusively rely and shall
         be full protected in acting or refraining from acting upon any
         resolution, certificate, statement, instrument, opinion, report,
         notice, request, direction, consent, order, bond, debenture, note,
         other evidence of indebtedness or other paper or document reasonably
         believed by it to be genuine and to have been signed, sent or presented
         by the proper party or parties.

                  (ii)     Any direction or act of the Guarantor contemplated by
         this Guarantee Agreement shall be sufficiently evidenced by an
         Officers' Certificate unless otherwise prescribed herein.

                  (iii)    Whenever, in the administration of this Guarantee
         Agreement, the


                                      -8-
<PAGE>   13

         Guarantee Trustee shall deem it desirable that a matter be proved or
         established before taking, suffering or omitting to take any action
         hereunder, the Guarantee Trustee (unless other evidence is herein
         specifically prescribed) may, in the absence of bad faith on its part,
         request and rely upon an Officers' Certificate which, upon receipt of
         such request from the Guarantee Trustee, shall be promptly delivered by
         the Guarantor.

                  (iv)     The Guarantee Trustee may consult with legal counsel,
         and the advice or opinion of such legal counsel with respect to legal
         matters shall be full and complete authorization and protection in
         respect of any action taken, suffered or omitted to be taken by it
         hereunder in good faith and in accordance with such advice or opinion.
         Such legal counsel may be legal counsel to the Guarantor or any of its
         Affiliates and may be one of its employees. The Guarantee Trustee shall
         have the right at any time to seek instructions concerning the
         administration of this Guarantee Agreement from any court of competent
         jurisdiction.

                  (v)      The Guarantee Trustee shall be under no obligation to
         exercise any of the rights or powers vested in it by this Guarantee
         Agreement at the request or direction of any Holder, unless such Holder
         shall have provided to the Guarantee Trustee such adequate security and
         indemnity satisfactory to it, against the costs, expenses (including
         attorneys' fees and expenses) and liabilities that might be incurred by
         it in complying with such request or direction, including such
         reasonable advances as may be requested by the Guarantee Trustee;
         provided that nothing contained in this Section 3.2(a)(v) shall be
         taken to relieve the Guarantee Trustee, upon the occurrence of an Event
         of Default, of its obligation to exercise the rights and powers vested
         in it by this Guarantee Agreement.

                  (vi)     The Guarantee Trustee shall not be bound to make any
         investigation into the facts or matters stated in any resolution,
         certificate, statement, instrument, opinion, report, notice, request,
         direction, consent, order, bond, debenture, note, other evidence of
         indebtedness or other paper or document, but the Guarantee Trustee, in
         its discretion, may make such further inquiry or investigation into
         such facts or matters as it may see fit.

                  (vii)    The Guarantee Trustee may execute any of the trusts
         or powers hereunder or perform any duties hereunder either directly or
         by or through its agents, attorneys custodians or nominees, and the
         Guarantee Trustee shall not be responsible for any misconduct or
         negligence on the part of any such agent, attorney custodians or
         nominees appointed with due care by it hereunder.

                  (viii)   Whenever in the administration of this Guarantee
         Agreement the Guarantee Trustee shall deem it desirable to receive
         instructions with respect to enforcing any remedy or right or taking
         any other action hereunder, the Guarantee Trustee (A) may request
         instructions from the Holders, (B) may refrain from enforcing such
         remedy or right or taking such other action until such instructions are
         received, and (C) shall be fully protected in acting in accordance with
         such instructions.


                                      -9-
<PAGE>   14

         (b)      No provision of this Guarantee Agreement shall be deemed to
impose any duty or obligation on the Guarantee Trustee to perform any act or
acts or exercise any right, power, duty or obligation conferred or imposed on it
in any jurisdiction in which it shall be illegal, or in which the Guarantee
Trustee shall be unqualified or incompetent in accordance with applicable law,
to perform any such act or acts or to exercise any such right, power, duty or
obligation. No permissive power or authority available to the Guarantee Trustee
shall be construed to be a duty to act in accordance with such power and
authority.


         SECTION 3.3.      INDEMNITY.

         The Guarantor agrees to indemnify the Guarantee Trustee for, and to
hold it harmless against, any loss, liability or expense incurred without
negligence, willful misconduct or bad faith on the part of the Guarantee
Trustee, arising out of or in connection with the acceptance or administration
of this Guarantee Agreement, including the costs and expenses of defending
itself against any claim or liability in connection with the exercise or
performance of any of its powers or duties hereunder. The provisions of this
Section shall survive the termination of this Guarantee Agreement or the
resignation or removal of the Guarantee Trustee. The Guarantee Trustee will not
claim or exact any lien or charge on any Guarantee Payments as a result of any
amount due to it under this Guarantee Agreement.

                          ARTICLE 4. GUARANTEE TRUSTEE


         SECTION 4.1.      GUARANTEE TRUSTEE: ELIGIBILITY.

         (a)      There shall at all times be a Guarantee Trustee which shall:

                  (i)      not be an Affiliate of the Guarantor; and

                  (ii)     be a Person that is eligible pursuant to the Trust
         Indenture Act to act as such and has a combined capital and surplus of
         at least $50,000,000, and shall be a corporation meeting the
         requirements of Section 310(a) of the Trust Indenture Act. If such
         corporation publishes reports of condition at least annually, pursuant
         to law or to the requirements of the supervising or examining
         authority, then, for the purposes of this Section 4.1 and to the extent
         permitted by the Trust Indenture Act, the combined capital and surplus
         of such corporation shall be deemed to be its combined capital and
         surplus as set forth in its most recent report of condition so
         published.

         (b)      If at any time the Guarantee Trustee shall cease to be
eligible to so act under Section 4.1(a), the Guarantee Trustee shall immediately
resign in the manner and with the effect set out in Section 4.2(c).


                                      -10-
<PAGE>   15

         (c)      If the Guarantee Trustee has or shall acquire any "conflicting
interest" within the meaning of Section 310(b) of the Trust Indenture Act, the
Guarantee Trustee and Guarantor shall in all respects comply with the provisions
of Section 310(b) of the Trust Indenture Act.


         SECTION 4.2.      APPOINTMENT, REMOVAL AND RESIGNATION OF THE GUARANTEE
TRUSTEE.

         (a)      Subject to Section 4.2(b), the Guarantee Trustee may be
appointed or removed without cause at any time by the Guarantor.

         (b)      The Guarantee Trustee shall not be removed until a Successor
Guarantee Trustee has been appointed and has accepted such appointment by
written instrument executed by such Successor Guarantee Trustee and delivered to
the Guarantor.

         (c)      The Guarantee Trustee appointed hereunder shall hold office
until a Successor Guarantee Trustee shall have been appointed or until its
removal or resignation. The Guarantee Trustee may resign from office (without
need for prior or subsequent accounting) by an instrument in writing executed by
the Guarantee Trustee and delivered to the Guarantor, which resignation shall
not take effect until a Successor Guarantee Trustee has been appointed and has
accepted such appointment by instrument in writing executed by such Successor
Guarantee Trustee and delivered to the Guarantor and the resigning Guarantee
Trustee.

         (d)      If no Successor Guarantee Trustee shall have been appointed
and accepted appointment as provided in this Section 4.2 within 60 days after
delivery to the Guarantor of an instrument of resignation, the resigning
Guarantee Trustee may petition, at the expense of the Guarantor, any court of
competent jurisdiction for appointment of a Successor Guarantee Trustee. Such
court may thereupon, after prescribing such notice, if any, as it may deem
proper, appoint a Successor Guarantee Trustee.

                              ARTICLE 5. GUARANTEE


         SECTION 5.1.      GUARANTEE.

         The Guarantor irrevocably and unconditionally agrees to pay in full to
the Holders the Guarantee Payments (without duplication of amounts theretofore
paid by or on behalf of the Issuer), as and when due, regardless of any defense,
right of set-off or counterclaim which the Issuer may have or assert, except the
defense of payment. The Guarantor's obligation to make a Guarantee Payment may
be satisfied by direct payment of the required amounts by the Guarantor to the
Holders or by causing the Issuer to pay such amounts to the Holders.


                                      -11-
<PAGE>   16

         SECTION 5.2.      WAIVER OF NOTICE AND DEMAND.

         The Guarantor hereby waives notice of acceptance of the Guarantee
Agreement and of any liability to which it applies or may apply, presentment,
demand for payment, any right to require a proceeding first against the
Guarantee Trustee, Issuer or any other Person before proceeding against the
Guarantor, protest, notice of nonpayment, notice of dishonor, notice of
redemption and all other notices and demands.


         SECTION 5.3.      OBLIGATIONS NOT AFFECTED.

         The obligations, covenants, agreements and duties of the Guarantor
under this Guarantee Agreement shall in no way be affected or impaired by reason
of the happening from time to time of any of the following:

         (a)      the release or waiver, by operation of law or otherwise, of
the performance or observance by the Issuer of any express or implied agreement,
covenant, term or condition relating to the Preferred Securities to be performed
or observed by the Issuer;

         (b)      the extension of time for the payment by the Issuer of all or
any portion of the Distributions (other than an extension of time for payment of
Distributions that results from the extension of any interest payment period on
the Debentures as provided in the Indenture), Redemption Price, Liquidation
Distribution or any other sums payable under the terms of the Preferred
Securities or the extension of time for the performance of any other obligation
under, arising out of, or in connection with, the Preferred Securities;

         (c)      any failure, omission, delay or lack of diligence on the part
of the Holders to enforce, assert or exercise any right, privilege, power or
remedy conferred on the Holders pursuant to the terms of the Preferred
Securities, or any action on the part of the Issuer granting indulgence or
extension of any kind;

         (d)      the voluntary or involuntary liquidation, dissolution, sale of
any collateral, receivership, insolvency, bankruptcy, assignment for the benefit
of creditors, reorganization, arrangement, composition or readjustment of debt
of, or other similar proceedings affecting, the Issuer or any of the assets of
the Issuer;

         (e)      any invalidity of, or defect or deficiency in, the Preferred
Securities;

         (f)      the settlement or compromise of any obligation guaranteed
hereby or hereby incurred; or

         (g)      any other circumstance whatsoever that might otherwise
constitute a legal or equitable discharge or defense of a guarantor, it being
the intent of this Section 5.3 that the obligations of the Guarantor hereunder
shall be absolute and unconditional under any and all circumstances.

         There shall be no obligation of the Holders to give notice to, or
obtain the consent of, the Guarantor with respect to the happening of any of the
foregoing.


                                      -12-
<PAGE>   17

         SECTION 5.4.      RIGHTS OF HOLDERS.

         The Guarantor expressly acknowledges that: (i) this Guarantee Agreement
will be deposited with the Guarantee Trustee to be held for the benefit of the
Holders; (ii) the Guarantee Trustee has the right to enforce this Guarantee
Agreement on behalf of the Holders; (iii) the Holders of a Majority in
Liquidation Amount of the Preferred Securities have the right to direct the
time, method and place of conducting any proceeding for any remedy available to
the Guarantee Trustee in respect of this Guarantee Agreement or exercising any
trust or power conferred upon the Guarantee Trustee under this Guarantee
Agreement; and (iv) any Holder may institute a legal proceeding directly against
the Guarantor to enforce its rights under this Guarantee Agreement, without
first instituting a legal proceeding against the Guarantee Trustee, the Issuer
or any other Person.


         SECTION 5.5.      GUARANTEE OF PAYMENT.

         This Guarantee Agreement creates a guarantee of payment and not of
collection. This Guarantee Agreement will not be discharged except by payment of
the Guarantee Payments in full (without duplication of amounts theretofore paid
by the Issuer) or upon distribution of Debentures to Holders as provided in the
Declaration.


         SECTION 5.6.      SUBROGATION.

         The Guarantor shall be subrogated to all (if any) rights of the Holders
against the Issuer in respect of any amounts paid to the Holders by the
Guarantor under this Guarantee Agreement and shall have the right to waive
payment by the Issuer pursuant to Section 5.1; provided, however, that the
Guarantor shall not (except to the extent required by mandatory provisions of
law) be entitled to enforce or exercise any rights which it may acquire by way
of subrogation or any indemnity, reimbursement or other agreement, in all cases
as a result of payment under this Guarantee Agreement, if, at the time of any
such payment, any amounts are due and unpaid under this Guarantee Agreement. If
any amount shall be paid to the Guarantor in violation of the preceding
sentence, the Guarantor agrees to hold such amount in trust for the Holders and
to pay over such amount to the Holders.


         SECTION 5.7.      INDEPENDENT OBLIGATIONS.

         The Guarantor acknowledges that its obligations hereunder are
independent of the


                                      -13-
<PAGE>   18

obligations of the Issuer with respect to the Preferred Securities and that the
Guarantor shall be liable as principal and as debtor hereunder to make Guarantee
Payments pursuant to the terms of this Guarantee Agreement notwithstanding the
occurrence of any event referred to in subsections (a) through (g), inclusive,
of Section 5.3 hereof.

                            ARTICLE 6. SUBORDINATION


         SECTION 6.1.      SUBORDINATION.

         The obligations of the Guarantor under this Guarantee Agreement will
constitute unsecured obligations of the Guarantor and will rank subordinate and
junior in right of payment to all Senior Debt of the Guarantor to the extent and
manner set forth in the Indenture. The obligations of the Guarantor under this
Guarantee Agreement do not constitute Senior Debt.


         SECTION 6.2.      PARI PASSU GUARANTEES.

         The obligations of the Guarantor under this Guarantee Agreement shall
rank pari passu with its obligations under (i) any similar guarantee agreements
issued by the Guarantor on behalf of the holders of preferred or common
securities issued by any Regions Trust (as defined in the Indenture); (ii) the
Indenture and the Securities (as defined therein) issued thereunder; (iii) the
Expense Agreement (as defined in the Declaration) and any similar expense
agreements entered into by the Guarantor in connection with the offering of
Preferred Securities (as defined in the Indenture) by any Regions Trust (as
defined in the Indenture), and (iv) any other security, guarantee or other
agreement or obligation that is expressly stated to rank pari passu with the
obligations of the Guarantor under this Guarantee Agreement or with any
obligation that ranks pari passu with the obligations of the Guarantor under
this Guarantee Agreement.

                             ARTICLE 7. TERMINATION


         SECTION 7.1.      TERMINATION.

         This Guarantee Agreement shall terminate and be of no further force and
effect upon (i) full payment of the Redemption Price of all Preferred
Securities, (ii) the distribution of Debentures to the Holders in exchange for
all of the Preferred Securities or (iii) full payment of the amounts payable in
accordance with the Declaration upon liquidation of the Issuer. Notwithstanding
the foregoing, this Guarantee Agreement will continue to be effective or will be
reinstated, as the case may be, if at any time any Holder must restore payment
of any sums paid with respect to Preferred Securities or this Guarantee
Agreement.


                                      -14-
<PAGE>   19

                            ARTICLE 8. MISCELLANEOUS


         SECTION 8.1.      SUCCESSORS AND ASSIGNS.

         All guarantees and agreements contained in this Guarantee Agreement
shall bind the successors, assigns, receivers, trustees and representatives of
the Guarantor and shall inure to the benefit of the Holders of the Preferred
Securities then outstanding. Except in connection with a consolidation, merger
or sale involving the Guarantor that is permitted under Article Eight of the
Indenture and pursuant to which the successor or assignee agrees in writing to
perform the Guarantor's obligations hereunder, the Guarantor shall not assign
its obligations hereunder.


         SECTION 8.2.      AMENDMENTS.

         Except with respect to any changes which do not adversely affect the
rights of the Holders in any material respect (in which case no consent of the
Holders will be required), this Guarantee Agreement may only be amended with the
prior approval of the Holders of not less than a Majority in Liquidation Amount
of the Preferred Securities. The provisions of Article VI of the Declaration
concerning meetings of the Holders shall apply to the giving of such approval.


         SECTION 8.3.      NOTICES.

         Any notice, request or other communication required or permitted to be
given hereunder shall be in writing, duly signed by the party giving such
notice, and delivered, telecopied or mailed by first class mail as follows:

         (a)      if given to the Guarantor, to the address set forth below or
such other address, facsimile number or to the attention of such other Person as
the Guarantor may give notice to the Holders:


                           Regions Financial Corporation
                           417 North 20th Street
                           Birmingham, Alabama 35203
                           Facsimile No.: 205-326-7751
                           Attention: General Counsel


         (b)      if given to the Issuer at the Issuer's address set forth below
with a copy to the Guarantee Trustee as set forth below:


                           Regions Financial Corporation
                           417 North 20th Street
                           Birmingham, Alabama 35203
                           Facsimile No.: 205-326-7751
                           Attention: General Counsel



                                      -15-
<PAGE>   20

         (c)      if given to the Guarantee Trustee:

                           Bankers Trust Company
                           4 Albany Street, 4th Floor
                           New York, New York 10006
                           Facsimile No.: (212) 250-6961/6392
                           Attention: Corporate Trust Administration

         (d)      if given to any Holder, at the address set forth on the books
and records of the Issuer.

         All notices hereunder shall be deemed to have been given when received
in person, telecopied with receipt confirmed, or mailed by first class mail,
postage prepaid, except that if a notice or other document is refused delivery
or cannot be delivered because of a changed address of which no notice was
given, such notice or other document shall be deemed to have been delivered on
the date of such refusal or inability to deliver.


         SECTION 8.4.      BENEFIT.

         This Guarantee Agreement is solely for the benefit of the Holders and
is not separately transferable from the Preferred Securities.


         SECTION 8.5.      GOVERNING LAW.

         THIS GUARANTEE AGREEMENT SHALL BE GOVERNED BY AND CONSTRUED AND
INTERPRETED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK.


         SECTION 8.6.      COUNTERPARTS.

         This instrument may be executed in any number of counterparts, each of
which so executed shall be deemed to be an original, but all such counterparts
shall together constitute but one and the same instrument.


                                      -16-
<PAGE>   21


         IN WITNESS WHEREOF, the undersigned have executed this Guarantee
Agreement as of the date first above written.

                                    REGIONS FINANCIAL CORPORATION

                                    By:
                                       ------------------------------
                                    Name:
                                         ----------------------------
                                    Title:
                                          ---------------------------

                                    BANKERS TRUST COMPANY,
                                    as Guarantee Trustee

                                    By:
                                       ------------------------------
                                    Name:
                                         ----------------------------
                                    Title:
                                          ---------------------------


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