Document:

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                                                                   EXHIBIT 10.25

                         EXHIBIT: TELPRI/PRTA AGREEMENT

                                  MAY 25, 2001

Puerto Rico Telephone Authority
c/o Government Development Bank
San Juan, Puerto Rico 00940
Attention:  President

Popular, Inc.
209 Munoz Rivera
Hato Rey, Puerto Rico 00918
Attention:  Carlos Vazquez

Ladies and Gentlemen:

                     RE: TELPRI/PRTA Shareholders Agreement

         Reference is made to the Shareholders Agreement dated as of March 2,
1999 (the "Agreement") among Telecomunicaciones de Puerto Rico, Inc. ("TELPRI"),
GTE Holdings (Puerto Rico) LLC ("Puerto Rico Holdings"), GTE International
Telecommunications Incorporated ("GITI"), Popular Inc ("Popular") and the Puerto
Rico Telephone Authority ("PRTA"). Capitalized terms used in this letter
agreement and not otherwise defined herein have the meanings assigned to them in
the Agreement.

         Verizon Communications Inc ("Verizon") and its wholly owned subsidiary
GTE Corporation ("GTE") have reorganized Verizon's and GTE's international
subsidiaries. As part of this reorganization, GITI is proposing to engage in a
transfer (the "Transfer") of all of the Purchaser Interest in Puerto Rico
Holdings to Verizon International Holdings Ltd. ("Verizon International"), a
Bermuda corporation. The Agreement permits transfers of Purchaser Interest to
wholly owned subsidiaries of GTE Corporation.

         Before and after the Transfer, Verizon will own indirectly 100% of
GITI. GITI will own indirectly over 98% of the stock (by vote and value) of
Verizon International. Less than 2% of Verizon International will be owned,
directly or indirectly, by third-party institutional investors as a result of
certain private placements. See the attached chart for a diagram of the
structure of Verizon's international subsidiaries before and after the Transfer.

         Please note that the Verizon-controlled entities are not disposing of
any shares of Voting Stock of TELPRI to third parties and intend to maintain the
ability to appoint a majority of the Board of Directors of TELPRI. In addition,
Puerto Rico Holdings is not issuing any Purchaser Interest; Verizon
International will replace GITI as the sole holder of the Purchaser Interests of
Puerto Rico Holdings; and GTE will own directly or indirectly greater than a
majority in vote and value of all equity and equity-linked securities of GITI
and Verizon International

         To the extent (if any) that such proposed Transfer requires the
approval or consent of PRTA or Popular, including pursuant to Sections 4.1,
10.11 or 10.15 of the Agreement, GITI request respectfully that the PRTA and
Popular consent to (i) the Transfer by GITI to Verizon International of all of
the Purchaser Interests of Puerto Rico Holdings and (ii) the continuation of
GITI as the Strategic Purchaser under the Agreement (except as provided in the
next paragraph).

         The Parties agree that from and after the Transfer all applicable
restrictions of Sections 4.1, 4.3, 4.4 and 10.15 of the Agreement which formerly
applied to GITI shall apply solely to Verizon International

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and that Verizon International shall be deemed, for purposes of the Agreement,
to be a GTE Permitted Transferee and a member of the Purchaser Group.

         GITI agrees that from and after the Transfer GITI (or another
wholly-owned subsidiary of Verizon) shall maintain direct or indirect beneficial
ownership prior to March 2, 2004 of at least 95% of Verizon International. In
addition, prior to March 2,2004, GTE Corporation agrees to maintain record and
beneficial ownership, directly or indirectly, of at least a majority in vote and
value of all equity or equity-linked securities of GITI and Verizon
International (and any subsequent GTE Permitted Transferees to whom Shares or
Purchaser Interest have been Transferred), unless otherwise consented to by the
Government Development Bank for Puerto Rico, which consent shall not be
unreasonably withheld.

         Each of the under signed further acknowledge and agree that Purchaser's
rights and obligations under other agreements, dated as of March 2, 1999,
between or among the Shareholders shall not be affected by the Transfer.

         If you agree to the terms and provisions of this letter agreement,
please evidence such agreements, to be effective as of the date above, by
executing and returning two counterparts of this letter agreement to J. Goodwin
Bennett at Verizon Communications, 1095 Avenue of the Americas, Room 3839, New
York, NY 10022 (Facsimile: (212) 354-3698; Telephone: (212) 395-0059). Upon
receipt of such counterparts and promptly after completion of the Transfer,
Verizon International will execute and deliver an agreement committing to be
bound by the Agreement (including the restrictions of Sections 4.1, 4.3, 4.4 and
10.15 that formerly applied to GITI as Strategic Purchaser).

         This letter agreement may be executed in any number of counterparts and
by different parties in separate counterparts, each of which when so executed
shall be deemed to be an original and all of which taken together shall
constitute one and the same agreement. Delivery of an executed counterpart of a
signature page to this letter agreement by facsimile shall be effective as
delivery of a manually executed counterpart of this letter agreement.

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         This letter agreement shall be governed by, and construed in accordance
with, the laws of Puerto Rico without giving effect to the principles of
conflicts of laws thereof.

                                            GTE INTERNATIONAL
                                            TELECOMMUNICATIONS INCORPORATED

                                            By:
                                               --------------------------------

ACKNOWLEDGED AND AGREED:

PUERTO RICO TELEPHONE AUTHORITY

By:

PRTA HOLDINGS CORPORATION

By:

POPULAR, INC.

By:

TELECOMUNICACIONES DE PUERTO RICO, INC.

By:

GTE HOLDINGS (PUERTO RICO) LLC

By:

GTE CORPORATION

By:

By:

cc:  Russell W. Parks, Jr.
     Manuel Pietrantoni
     Brunilda Santos de Alvarez
     Jon Slater
     Howard Svigals
     Donald J. Toumey
     Matias Vega

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         This letter agreement shall be governed by, and construed in accordance
with, the laws of Puerto Rico without giving effect to the principles of
conflicts of laws thereof.

                                      GTE INTERNATIONAL
                                      TELECOMMUNICATIONS INCORPORATED

                                      By:
                                         ----------------------------------

ACKNOWLEDGED AND AGREED:

PUERTO RICO TELEPHONE AUTHORITY

By:

PRTA HOLDINGS CORPORATION

By:

POPULAR, INC.

By:

TELECOMUNICACIONES DE PUERTO RICO, INC.

By:

GTE HOLDINGS (PUERTO RICO) LLC

By:

GTE CORPORATION

By:

By:

cc:  Russell W. Parks, Jr.
     Manuel Pietrantoni
     Brunilda Santos de Alvarez
     Jon Slater
     Howard Svigals
     Donald J. Toumey
     Matias Vega

                                                                               4
<PAGE>   5

         This letter agreement shall be governed by, and construed in accordance
with, the laws of Puerto Rico without giving effect to the principles of
conflicts of laws thereof.

                                 GTE INTERNATIONAL
                                 TELECOMMUNICATIONS INCORPORATED

                                 By:
                                    ------------------------------

ACKNOWLEDGED AND AGREED:

PUERTO RICO TELEPHONE AUTHORITY

By:

PRTA HOLDINGS CORPORATION

By:

POPULAR, INC.

By:

TELECOMUNICACIONES DE PUERTO RICO, INC.

By:

GTE HOLDINGS (PUERTO RICO) LLC

By:

GTE CORPORATION

By:

By:

cc:  Russell W. Parks, Jr.
     Manuel Pietrantoni
     Brunilda Santos de Alvarez
     Jon Slater
     Howard Svigals
     Donald J. Toumey
     Matias Vega

                                                                               5
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         This letter agreement shall be governed by, and construed in accordance
with, the laws of Puerto Rico without giving effect to the principles of
conflicts of laws thereof.

                                 GTE INTERNATIONAL
                                 TELECOMMUNICATIONS INCORPORATED

                                 By:
                                    ------------------------------

ACKNOWLEDGED AND AGREED:

PUERTO RICO TELEPHONE AUTHORITY

By:

PRTA HOLDINGS CORPORATION

By:

POPULAR, INC.

By:

TELECOMUNICACIONES DE PUERTO RICO, INC.

By:

GTE HOLDINGS (PUERTO RICO) LLC

By:

GTE CORPORATION

By:

By:

cc:  Russell W. Parks, Jr.
     Manuel Pietrantoni
     Brunilda Santos de Alvarez
     Jon Slater
     Howard Svigals
     Donald J. Toumey
     Matias Vega

                                                                               6<PAGE>   1
                                                                    EXHIBIT 10.1

                       TWENTY-FIRST AMENDMENT TO THE THIRD
                        AMENDED AND RESTATED AGREEMENT OF
                  LIMITED PARTNERSHIP OF AIMCO PROPERTIES, L.P.

         This TWENTY-FIRST AMENDMENT TO THE THIRD AMENDED AND RESTATED AGREEMENT
OF LIMITED PARTNERSHIP OF AIMCO PROPERTIES, L.P., dated as of May 10, 2001 (this
"Amendment"), is being executed by AIMCO-GP, Inc., a Delaware corporation (the
"General Partner"), as the general partner of AIMCO Properties, L.P., a Delaware
limited partnership (the "Partnership"), pursuant to the authority conferred on
the General Partner by the Third Amended and Restated Agreement of Limited
Partnership of AIMCO Properties, L.P., dated as of July 29, 1994, as amended
and/or supplemented from time to time (the "Agreement"). Capitalized terms used,
but not otherwise defined herein, shall have the respective meanings ascribed
thereto in the Agreement.

         NOW, THEREFORE, in consideration of the foregoing, and other good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the parties hereto agree as follows:

         1. The definition of "Majority in Interest of the Limited Partners" in
Article I of the Agreement is amended to read in its entirety as follows:

                           "Majority in Interest of the Limited Partners" means
         Limited Partners (other than (i) the Special Limited Partner and (ii)
         any Limited Partner fifty percent (50%) or more of whose equity is
         owned, directly or indirectly, by (a) the General Partner or (b) any
         REIT as to which the General Partner is a "qualified REIT subsidiary"
         (within the meaning of Code Section 856(i)(2))) holding more than fifty
         percent (50%) of the outstanding Voting Units (as defined below) held
         by all Limited Partners (other than (i) the Special Limited Partner and
         (ii) any Limited Partner fifty percent (50%) or more of whose equity is
         owned, directly or indirectly, by (a) the General Partner or (b) any
         REIT as to which the General Partner is a "qualified REIT subsidiary"
         (within the meaning of Code Section 856(i)(2))). For purposes of this
         definition, "Voting Units" means Partnership Common Units, Class I High
         Performance Partnership Units and any other class of Partnership Units
         having the same voting or approval rights as Partnership Common Units.

         2. The Partnership Unit Designation of the Class I Partnership
Preferred Units of AIMCO Properties, L.P. (Exhibit Q to the Agreement) is hereby
amended to (i) remove from Section 2 the definition of "Majority in Interest of
the Limited Partners" and (ii) to remove the second sentence from Section 10.

         3. The Partnership Unit Designation of the Class Two Partnership
Preferred Units of AIMCO Properties, L.P. (Exhibit R to the Agreement) is hereby
amended to (i) remove from Section 2 the definition of "Majority in Interest of
the Limited Partners" and (ii) to remove the second sentence from Section 10.

         4. The Partnership Unit Designation of the Class Four Partnership
Preferred Units of AIMCO Properties, L.P. (Exhibit T to the Agreement) is hereby
amended to (i) remove from Section 2 the definition of "Majority in Interest of
the Limited Partners" and (ii) to remove the second sentence from Section 11.

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         5. The Partnership Unit Designation of the Class Three Partnership
Preferred Units of AIMCO Properties, L.P. (Exhibit U to the Agreement) is hereby
amended to (i) remove from Section 3 the definition of "Majority in Interest of
the Limited Partners" and (ii) to remove the second sentence from Section 10.

         6. The Partnership Unit Designation of the Class Five Partnership
Preferred Units of AIMCO Properties, L.P. (Exhibit V to the Agreement) is hereby
amended to (i) remove from Section 2 the definition of "Majority in Interest of
the Limited Partners" and (ii) to remove the second sentence from Section 9.

         7. The Partnership Unit Designation of the Class Six Partnership
Preferred Units of AIMCO Properties, L.P. (Exhibit X to the Agreement) is hereby
amended to (i) remove from Section 2 the definition of "Majority in Interest of
the Limited Partners" and (ii) to remove the second sentence from Section 11.

         8. The Partnership Unit Designation of the Class Seven Partnership
Preferred Units of AIMCO Properties, L.P. (Exhibit AA to the Agreement) is
hereby amended to (i) remove from Section 2 the definition of "Majority in
Interest of the Limited Partners" and (ii) to remove the second sentence from
Section 10.

         9. The Partnership Unit Designation of the Class Eight Partnership
Preferred Units of AIMCO Properties, L.P. (Exhibit BB to the Agreement) is
hereby amended to (i) remove from Section 2 the definition of "Majority in
Interest of the Limited Partners" and (ii) to remove the second sentence from
Section 9.

         10. Except as specifically amended hereby, the terms, covenants,
provisions and conditions of the Agreement shall remain unmodified and continue
in full force and effect and, except as amended hereby, all of the terms,
covenants, provisions and conditions of the Agreement are hereby ratified and
confirmed in all respects.

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         IN WITNESS WHEREOF, this Amendment has been executed as of the date
first written above.

                                            GENERAL PARTNER:

                                            AIMCO-GP, INC.

                                            By: /s/ JOEL F. BONDER
                                               --------------------------------
                                               Name:  Joel F. Bonder
                                               Title: Executive Vice President

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