Exhibit 4.13





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                        FIRST AMENDMENT TO LOAN AGREEMENT



                          Dated as of February 1, 2004

                                     Between

         STATE ENVIRONMENTAL IMPROVEMENT AND ENERGY RESOURCES AUTHORITY



                                       and



                      UNION ELECTRIC COMPANY, DBA AMERENUE
                  ---------------------------------------------
                     Supplementing and amending that certain
                                 Loan Agreement
                          dated as of September 1, 1998


                                   $50,000,000
         State Environmental Improvement and Energy Resources Authority
                Environmental Improvement Revenue Refunding Bonds
                        (Union Electric Company Project)
                                  Series 1998C
                  ---------------------------------------------






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<PAGE>



                        FIRST AMENDMENT TO LOAN AGREEMENT
                            ------------------------


                                TABLE OF CONTENTS

 (This Table of Contents is not a part of the First Amendment to Loan Agreement
                   and is only for convenience of reference.)

<TABLE>
<CAPTION>

SECTION                                                HEADING                                                   PAGE
<S>    <C>                <C>
ARTICLE I                  DEFINITIONS............................................................................2

       Section 1.01.       Definitions of Terms...................................................................2

ARTICLE II                 AMENDMENTS TO ORIGINAL AGREEMENT.......................................................2

       Section 2.01.       Amendment to Article III of the Original Agreement.....................................2
       Section 2.02.       Amendments to Article V of the Original Agreement......................................2
       Section 2.03.       Amendments to Article VI of the Original Agreement.....................................6
       Section 2.04.       Amendment to Section 8.1 of the Original Agreement.....................................7
       Section 2.05.       Amendments to Article IX of the Original Agreement.....................................7
       Section 2.06.       Amendments to Section 10.4 of the Original Agreement...................................8

ARTICLE III                MISCELLANEOUS..........................................................................8

       Section 3.01.       Agreement Confirmed....................................................................8
       Section 3.02.       Severability...........................................................................8
       Section 3.03.       Counterparts...........................................................................8
       Section 3.04.       Applicable Provisions of Law...........................................................8
       Section 3.05.       Effective Date.........................................................................8

</TABLE>

                                       i

<PAGE>


                        FIRST AMENDMENT TO LOAN AGREEMENT

     THIS FIRST AMENDMENT TO LOAN AGREEMENT (this "First Amendment") is made and
entered into as of February 1, 2004 between the STATE ENVIRONMENTAL  IMPROVEMENT
AND ENERGY  RESOURCES  AUTHORITY of the State of Missouri,  a body corporate and
politic  and a  governmental  instrumentality  of the  State  of  Missouri  (the
"Issuer"),  and UNION ELECTRIC COMPANY, a Missouri corporation doing business as
AMERENUE (the "Company"):


                                   WITNESSETH:

     WHEREAS,   on  September  4,  1998  the  Issuer  issued  its  Environmental
Improvement  Revenue  Refunding  Bonds (Union Electric  Company  Project) Series
1998BC (the "Bonds") in the original  aggregate  principal amount of $50,000,000
pursuant to an Indenture  of Trust dated as of September 1, 1998 (the  "Original
Indenture") by and between the Issuer and UMB Bank & Trust,  N.A.,  successor to
State Street Bank and Trust Company of Missouri, N.A. (the "Trustee"); and

     WHEREAS,  in connection with the issuance of the Bonds,  the Issuer and the
Company  executed and delivered the Loan Agreement dated as of September 1, 1998
by and between the Issuer and the Company (the "Original Agreement"); and

     WHEREAS,  the  Original  Indenture  is being  amended  and  restated by the
Amended and Restated  Indenture  of Trust of even date  herewith in order to add
provisions  relating to a bond insurance  policy for the Bonds and to permit the
delivery to the Trustee by the Company of its mortgage  bonds to further  secure
the Bonds; and

     WHEREAS,  Section 11.01 of the Original  Indenture provides that the Issuer
and the Company may,  without notice to or the consent of any Bondholder,  enter
into an  agreement  supplemental  to the  Original  Agreement to make changes in
connection  with any authorized  amendment or supplement to the  Indenture,  and
Section 10.4 of the Original Agreement provides that such supplemental agreement
is subject to the written consent of the Trustee; and

     WHEREAS,  the  Issuer  and the  Company  desire to enter  into  this  First
Amendment,  as permitted by Section 11.01 of the Original  Indenture and Section
10.4 of the Original Agreement, in order to amend the Original Agreement to make
certain  changes  relating  to  the  amendments  being  made  to  the  Indenture
concurrently herewith;

     NOW,  THEREFORE,  in  consideration  of the  foregoing  and  of the  mutual
covenants herein set forth, the parties hereto agree as follows:

<PAGE>


                                    ARTICLE I

                                   DEFINITIONS

     Section  1.01.  Definitions  of  Terms.  For all  purposes  of  this  First
Amendment, in addition to the terms defined above in the WHEREAS clauses, unless
the context clearly  requires  otherwise,  all terms defined in Article I of the
Indenture have the same meanings in this First Amendment.


                                                    ARTICLE II

                                         AMENDMENTS TO ORIGINAL AGREEMENT

        Section 2.01. Amendment to Article III of the Original Agreement. The
last clause of Section 3.5 of the Original Agreement is hereby amended to read
as follows:

                    ", provided that the Trustee and the Bond Insurer  receive a
                    Favorable Opinion of Tax Counsel prior to such abandonment."

     Section  2.02.  Amendments  to  Article V of the  Original  Agreement.  (a)
Subsection  5.1(a)  of the  Original  Agreement  is  hereby  amended  to read as
follows:

                    "(a)  The  Company  will  repay  the  loan  made to it under
                    Section 4.1 as follows:  Before the close of business (local
                    time at the principal  corporate office of the Registrar) on
                    the day  before  each day on which  any  payment  of  either
                    principal of or interest on the Bonds, or both, shall become
                    due (whether at maturity, or upon redemption or acceleration
                    or   otherwise),   the  Company  will  pay,  in  immediately
                    available funds, an amount which, together with other moneys
                    held  by the  Tender  Agent  or by  the  Trustee  under  the
                    Indenture and available therefor,  will enable the Registrar
                    to make such payment in full in a timely manner. If such day
                    on which any payment shall become due is not a Business Day,
                    then the payment  required by this Section  shall be made on
                    or  before  the  preceding  Business  Day.  If  the  Company
                    defaults  in any  payment  required  by  this  Section,  the
                    Company will pay interest (to the extent  allowed by law) on
                    such  amount  until  paid at the  rate  provided  for in the
                    Bonds."

          (b) The last  paragraph  of Section 5.1 of the  Original  Agreement is
     hereby amended to read as follows:

                         "All amounts  payable under this Section by the Company
                    are  assigned by the Issuer to the  Trustee  pursuant to the
                    Indenture  for the benefit of the  Bondholders  and the Bond
                    Insurer.   The

                                      -2-

<PAGE>

                    Company  consents  to  such  assignment.   Accordingly,  the
                    Company will pay directly to the  Registrar at its principal
                    corporate  trust office all payments  payable by the Company
                    pursuant to this Section."

               (c) There is hereby  added a new  paragraph to the end of Section
          5.1 of the Original Agreement to read as follows:

                         "The Company  agrees to make all  payments  when due on
                    the First Mortgage  Bonds. If for any reason amounts paid to
                    the Trustee on the First Mortgage Bonds, together with other
                    moneys held by the Trustee and  available  for that purpose,
                    would not be sufficient to make the  corresponding  payments
                    of principal of, premium,  if any, and interest on the Bonds
                    corresponding   to  such  First  Mortgage  Bonds  when  such
                    payments  become  due,  the  Company  will  pay the  amounts
                    required from time to time to make up any such deficiency."

               (d) A new Subsection 5.2(d) is hereby added to the end of Section
          5.2 of the Original Agreement to read as follows:

                         "(d)   Notwithstanding  any  provision  herein  to  the
                    contrary,  payment to the Bond  Insurer of all  amounts  due
                    under the Insurance  Agreement  pursuant to the terms of the
                    Insurance Agreement."

               (e) Section 5.3 of the Original  Agreement  is hereby  amended to
          read as follows:

                         "Section 5.3. Prepayments.  The Company may at any time
                    prepay  to the  Registrar  all or any  part  of the  amounts
                    payable under Section 5.1. A prepayment will not relieve the
                    Company of its  obligations  under this Loan Agreement until
                    all the Bonds have been paid or provision for the payment of
                    all the Bonds has been made in accordance with the Indenture
                    and all amounts due the Bond Insurer have been paid.  In the
                    event of a mandatory  redemption  of the Bonds,  the Company
                    will prepay all amounts necessary for such redemption."

               (f) Section 5.4 of the Original  Agreement  is hereby  amended to
          read as follows:

                         "Section 5.4. Obligations of Company Unconditional. The
                    Company  agrees that the  obligations of the Company to make
                    the payments required by Sections 5.1 and 5.3 and to perform
                    its other agreements  contained in this Loan Agreement shall
                    be absolute and  unconditional.  Until the  principal of and
                    interest  on the  Bonds  shall  have  been  fully  paid,  or
                    provision  for the  payment

                                      -3-

<PAGE>

                    of the Bonds made in accordance with the Indenture,  and the
                    Bond  Insurer  is paid in  full,  the  Company  (a) will not
                    suspend or discontinue any payments  provided for in Section
                    5.1, (b) will perform all its other  agreements in this Loan
                    Agreement and (c) will not terminate this Loan Agreement for
                    any  cause  including  any  acts or  circumstances  that may
                    constitute  failure  of  consideration,  destruction  of  or
                    damage to the Project,  commercial  frustration  of purpose,
                    any change in the laws of the United  States or of the State
                    or any political subdivision of either or any failure of the
                    Issuer to perform any of its agreements,  whether express or
                    implied,  or any duty,  liability or obligation arising from
                    or connected with this Loan Agreement."

               (g) Section 5.5,  Section 5.6 and Section 5.7 are hereby added to
          the end of Article V of the Original Agreement to read as follows:

                         "Section 5.5. First Mortgage  Bonds.  The Company shall
                    execute  and  deliver to the  Trustee,  as  assignee  of the
                    Issuer,  its  First  Mortgage  Bonds.  The form of the First
                    Mortgage  Bonds  will be  substantially  as set forth in the
                    Company's  Supplemental  Indenture to its Mortgage  executed
                    and delivered to the Trustee on the  effective  date of this
                    First Amendment."

                         "Section 5.6. Payment of the Bonds from Payments of the
                    First  Mortgage   Bonds  and  Other  Amounts.   Payments  of
                    principal  of, and  premium,  if any,  and  interest on, the
                    First  Mortgage  Bonds by the  Company  to the  Trustee,  as
                    assignee of the Issuer,  shall  constitute  payments of such
                    amounts on the loan under Section  5.1(a) or of the purchase
                    price for the Bonds under Section 5.1(b). The Bonds shall be
                    payable from  payments made by the Company to the Trustee of
                    principal and interest on the First Mortgage Bonds delivered
                    hereunder.  Payments of principal of or premium,  if any, or
                    interest  on, or the  purchase  price  for,  the Bonds  with
                    moneys held under the  Indenture  for such payment  shall be
                    deemed  to be  like  payments  with  respect  to  the  First
                    Mortgage  Bonds.  The  obligations  of the  Company  to make
                    payments  under the First  Mortgage  Bonds shall be absolute
                    and  unconditional.  Whenever  the Bonds are  redeemable  in
                    whole or in part,  the Issuer  will redeem the same upon the
                    request of the Company, and the Company covenants and agrees
                    to pay an amount equal to the applicable redemption price of
                    the Bonds as a  prepayment  of principal of and interest due
                    on the First  Mortgage  Bonds.  If the  Company  prepays the
                    First  Mortgage  Bonds,  the  Company's   obligations  under
                    Section  5.1  will  be   satisfied   and  there  will  be  a
                    corresponding  redemption of the Bonds.  Whenever payment or
                    provision therefor has been made in respect of the principal
                    of or

                                      -4-

<PAGE>

                    interest  on all or any  portion of the Bonds in  accordance
                    with the Indenture  (whether at maturity or upon  redemption
                    or  acceleration),  the First Mortgage Bonds shall be deemed
                    paid to the extent such  payment or  provision  therefor has
                    been made and is  considered to be a payment of principal or
                    interest on the Bonds.  If the Bonds or any portion  thereof
                    are thereby  deemed paid in full,  First Mortgage Bonds in a
                    principal  amount equal to the principal amount of the Bonds
                    so deemed to be paid shall be cancelled  and returned to the
                    Company.  Subject to the  foregoing or unless the Company is
                    entitled  to a  credit  under  this  Loan  Agreement  or the
                    Indenture, all payments shall be in the full amount required
                    under the First Mortgage Bonds.

                         The  Issuer,  by  the  terms  of the  Indenture,  shall
                    require  the  Trustee  to notify  in  writing  the  Mortgage
                    Trustee of all payments or credits with respect to the First
                    Mortgage Bonds.

                         All First  Mortgage  Bonds  shall  equally  and ratably
                    secure all outstanding Bonds."

                         "Section 5.7.  Assignment  of Issuer's  Rights to First
                    Mortgage  Bonds.  As security  for the payment of its Bonds,
                    the Issuer  hereby  pledges  and  assigns to the Trustee the
                    First  Mortgage  Bonds  and the  right to  receive  payments
                    thereunder.  The Issuer directs the Company, and the Company
                    agrees,  to pay to the  Trustee at its  principal  corporate
                    trust office all payments on the First Mortgage  Bonds,  and
                    other payments due and payable to the Trustee hereunder. The
                    Company will make payments  directly to the Trustee  without
                    defense  or  set-off by reason of any  dispute  between  the
                    Company  and the Trustee or the  Issuer.  The Issuer  hereby
                    agrees that the Trustee as assignee  may enforce any and all
                    rights and remedies hereunder, but retains the right to also
                    proceed  in  its  own  name  against  the  Company  for  the
                    enforcement of the specific performance of any obligation of
                    the Company under Sections 5.2, 7.2 and 9.3; provided,  that
                    in any such action seeking specific performance,  the Issuer
                    shall  have no rights  with  respect  to the First  Mortgage
                    Bonds and in such  event the  obligation  of the  Company to
                    make the payments  required to repay the loan  hereunder and
                    the purchase price for the Bonds and payments required under
                    the First  Mortgage  Bonds  shall  remain  unconditional  as
                    provided in Section 5.4.

                         The Issuer and the Company  covenant and agree that the
                    First  Mortgage  Bonds  will at all  times  be (i) in  fully
                    registered   (both   principal  and  interest)   form;  (ii)
                    registered    in   the   name   of   the   Trustee;    (iii)
                    non-transferable  except as  provided in the  Mortgage;

                                      -5-

<PAGE>

                    and  (iv)  appropriately  marked  to  indicate  clearly  the
                    restrictions  on the transfer  thereof  imposed by this Loan
                    Agreement."

     Section  2.03.  Amendments  to Article VI of the  Original  Agreement.  (a)
Section 6.1 of the Original Agreement is hereby amended to read as follows:

                         "Section 6.1.  Maintenance  of  Existence.  The Company
                    agrees  that during the term of this Loan  Agreement  and so
                    long  as any  Bond is  outstanding,  it  will  maintain  its
                    corporate  existence,  will continue to be a corporation  in
                    good standing under the laws of the State, will not dissolve
                    or  otherwise  dispose  of all or  substantially  all of its
                    assets and will not  consolidate  with or merge into another
                    legal  entity or permit  one or more  other  legal  entities
                    (other  than one or more  subsidiaries  of the  Company)  to
                    consolidate  with or  merge  into it,  or sell or  otherwise
                    transfer to another  legal entity all or  substantially  all
                    its assets as an entirety and dissolve, unless the Company's
                    actions shall be permitted  under the terms of the Insurance
                    Agreement   and   (a)  in  the   case  of  any   merger   or
                    consolidation,  the Company is the surviving corporation, or
                    (b)(i) the surviving,  resulting or transferee  legal entity
                    is  organized  and  existing  under  the laws of the  United
                    States, a state thereof or the District of Columbia, and (if
                    not the Company)  assumes in writing all the  obligations of
                    the Company under this Loan Agreement,  the Mortgage and the
                    First Mortgage Bonds and (ii) no event which constitutes, or
                    which with the giving of notice or the lapse of time or both
                    would constitute an Event of Default shall have occurred and
                    be continuing  immediately after such merger,  consolidation
                    or transfer."

          (b) A new  sentence  is hereby  added to the end of Section 6.2 of the
     Original Agreement to read as follows:

                    "A copy of each such report furnished to the Trustee will be
                    filed with the Bond Insurer."

          (c) The second  paragraph of Section 6.5 of the Original  Agreement is
     hereby amended to read as follows:

                         "The Company  covenants  and agrees to notify  promptly
                    the Trustee,  Issuer and the Bond Insurer of the  occurrence
                    of any event of which the Company has notice and which event
                    would   require  the  Company  to  prepay  the  amounts  due
                    hereunder  because of a redemption upon a  determination  of
                    taxability."

          (d) Section 6.7 of the Original Agreement is hereby deleted.


                                      -6-

<PAGE>

          (e) Section 6.9 of the Original Agreement is hereby amended to read as
     follows:

                    "The Company  shall not purchase or otherwise  acquire Bonds
                    without the prior written consent of the Bond Insurer unless
                    the Company  redeems or cancels such Bonds on the day of any
                    such purchase."

     Section 2.04.  Amendment to Section 8.1 of the Original Agreement.  Section
8.1 of the Original Agreement is hereby amended to read as follows:

                    "The  Company  may assign its rights and  obligations  under
                    this Loan  Agreement  with the prior written  consent of the
                    Issuer and the Bond Insurer,  but no assignment will relieve
                    the Company from primary liability for any obligations under
                    this Loan Agreement."

     Section 2.05.  Amendments to Article IX of the Original Agreement.  (a) The
first  paragraph of Section 9.1 of the Original  Agreement is hereby  amended to
read as follows:

                         "Whenever  any Event of Default under the Indenture has
                    occurred  and is  continuing,  the  Trustee  may,  with  the
                    consent of the Bond Insurer and shall, upon direction of the
                    Bond Insurer,  take whatever action may appear  necessary or
                    desirable to collect the payments then due and to become due
                    or to enforce performance of any agreement of the Company in
                    this Loan Agreement or in the First Mortgage Bonds."

          (b) The last  paragraph  of Section 9.1 of the  Original  Agreement is
     hereby amended to read as follows:

                         "Except  as  may   otherwise  be  provided   under  the
                    Mortgage,  nothing in this Loan Agreement shall be construed
                    to permit the Issuer,  the Trustee,  any  Bondholder  or any
                    receiver in any  proceeding  brought  under the Indenture to
                    take possession of or exclude the Company from possession of
                    the  Project  by  reason  of the  occurrence  of an Event of
                    Default."

          (c) Section 9.2 of the Original Agreement is hereby amended to read as
     follows:

                         "Section 9.2.  Delay Not Waiver;  Remedies.  A delay or
                    omission by the Issuer,  the Bond  Insurer or the Trustee in
                    exercising  any  right or remedy  accruing  upon an Event of
                    Default shall not impair the right or remedy or constitute a
                    waiver of or acquiescence in the Event of Default. No remedy
                    is exclusive of any other remedy. All available remedies are
                    cumulative."

                                      -7-

<PAGE>

     Section  2.06.  Amendments  to  Article X of the  Original  Agreement.  (a)
Section 10.4 of the Original Agreement is hereby amended to read as follows:

                    "After the issuance of the Bonds,  this Loan  Agreement  may
                    not be effectively amended or terminated without the written
                    consent  of the  Trustee,  the Bond  Insurer  and the Tender
                    Agent  and  in  accordance   with  the   provisions  of  the
                    Indenture."

          (b)  Section  10.11 is  hereby  added to the end of  Article  X of the
     Original Agreement to read as follows:

                         "Section  10.11.  Third  Party  Beneficiary.  The  Bond
                    Insurer  is  a  third   party   beneficiary   of  this  Loan
                    Agreement."


                                   ARTICLE III

                                  MISCELLANEOUS

     Section  3.01.  Agreement  Confirmed.  Except  as  amended  by  this  First
Amendment,  all of the provisions of the Original Agreement shall remain in full
force and effect,  and from and after the effective date of this First Amendment
shall be deemed to have been amended as herein set forth.

     Section 3.02. Severability.  If any provision of this First Amendment shall
be held or deemed to be or shall,  in fact, be inoperative or  unenforceable  as
applied in any particular case in any  jurisdiction or  jurisdictions  or in all
jurisdictions,  or in all cases because it conflicts with any other provision or
provisions  hereof or any  constitution or statute or rule of public policy,  or
for any other reason,  such circumstances shall not have the effect of rendering
the  provision in question  inoperative  or  unenforceable  in any other case or
circumstance, or of rendering any other provision or provisions herein contained
invalid, inoperative, or unenforceable to any extent whatever.

     Section 3.03.  Counterparts.  This First  Amendment  may be  simultaneously
executed in several counterparts,  each of which shall be an original and all of
which shall constitute but one and the same instrument.

     Section 3.04.  Applicable  Provisions of Law. This First Amendment shall be
governed by and construed in accordance with the laws of the State of Missouri.

     Section 3.05.  Effective Date. This First Amendment shall become  effective
on the date the Trustee has received the consent of the Trustee to the execution
hereof.


                                      -8-


<PAGE>




     IN WITNESS  WHEREOF,  the Issuer and the  Company  have  caused  this First
Amendment to be executed in their respective corporate names, and the Issuer has
caused its seal to be  hereunto  affixed  and  attested  by its duly  authorized
officer, all as of the date first above written.

                                    STATE ENVIRONMENTAL IMPROVEMENT AND
                                      ENERGY RESOURCES AUTHORITY


                                    By /s/ Charles D. Banks
                                      ------------------------------------------
                                                       Chairman


[SEAL]

ATTEST:

By /s/ Deron L. Cherry
  --------------------------------
             Secretary

                                    UNION ELECTRIC COMPANY, DBA AMERENUE


                                    By: /s/ Jerre E. Birdsong
                                      ------------------------------------------
                                    Title:  Vice President and Treasurer


                                      -9-


<PAGE>






                             CONSENT OF THE TRUSTEE

     Pursuant  to  Section  10.4  of  the  Loan  Agreement   between  the  State
Environmental  Improvement  and  Energy  Resources  Authority  of the  State  of
Missouri (the "Issuer") and Union Electric Company dba AmerenUE (the "Company"),
dated as of September 1, 1998, UMB Bank & Trust, N.A., successor to State Street
Bank and Trust  Company of Missouri,  N.A., as Trustee,  hereby  consents to the
execution  and  delivery of the First  Amendment to Loan  Agreement  dated as of
February 1, 2004 between the Issuer and the Company.


                                    UMB BANK & TRUST, N.A., successor to State
                                      Street Bank and Trust Company of Missouri,
                                      N.A.



                                    By /s/ Rebecca A. Dengler
                                      ------------------------------------------
                                      Its  Authorized Officer

Date:  February 24, 2004