Document:

<PAGE>
                                                                    Exhibit 4.28

                              SIXTH AMENDMENT FOR
                              DEVELOPMENT CONTRACT
                            PSTN EXCELLENCE REGIONAL
                               JUNCTION DIVRE II

--------------------------------------------------------------------------------

                       NUMBER: PKS.87/HK.820/TCC-00/2003
                             DATE: 09 OCTOBER 2003

                                    BETWEEN

                         PERUSAHAAN PERSEROAN (PERSERO)
                        PT TELEKOMUNIKASI INDONESIA, TBK

                                      AND

                         CONSORTIUM OLEX-LUCENT-BRIMBUN

<PAGE>
                                SIXTH AMENDMENT
                                      FOR
                              DEVELOPMENT CONTRACT
                            PSTN EXCELLENCE REGIONAL
                               JUNCTION DIVRE-II
                                    BETWEEN
                         PERUSAHAAN PERSEROAN (PERSERO)
                       PT. TELEKOMUNIKASI INDONESIA, TBK.
                                      AND
                         CONSORTIUM OLEX-LUCENT-BRIMBUN

--------------------------------------------------------------------------------
                       NUMBER: PKS.87/HK.820/TCC-00/2003

On this day NINTH of OCTOBER, year TWO THOUSAND THREE, placed at Jakarta,
between the concerned parties:

I.   PERUSAHAAN PERSEROAN (PERSERO) PT. TELEKOMUNIKASI INDONESIA, TBK.,
     telecommunications services and network provider established and
     incorporated under the law of Republic of Indonesia, having its address at
     Jalan Japati No. 1 Bandung 40133, in this legal act represent by, TRI
     DJATMIKO, HEAD OF CONSTRUCTION CENTER, based on the Power of Attorney of
     President Director Number: K.TEl. 107/HK510/UTA-00/02 dated 15 August 2002,
     hereinafter referred to as TELKOM.

II.  CONSORTIUM OLEX - LUCENT - BRIMBUN, a consortium formed under Notarial Deed
     No. 9 dated 14th December 2001, by Notary Benny Djaja, SH, SE, MM., and as
     amended under Notarial Deed No. 20 dated 8th September 2003 by Notary
     Imelda Nur Pane, SH, having its address at Wisma Bisnis Indonesia 15th
     Floor, Jl. Letjen S. Parman Kav. 12, Jakarta-11480; whereas in this legal
     act to be represented by FADJAR TJOANDA, hereinafter referred to as
     PARTNER.

     CONSORTIUM OLEX - LUCENT - BRIMBUN consist of:

                                       1
<PAGE>
     PT. OLEX CABLES INDONESIA, having its address at Wisma Bisnis Indonesia
     15th Floor, Jakarta, as CONSORTIUM LEADER hereinafter referred to as OLEX.

     LUCENT TECHNOLOGIES SINGAPORE PTE LTD, having its address at
     Technopark@Chai Chee, 750 D Chai Chee Road, Singapore 469004, as CONSORTIUM
     MEMBER, hereinafter referred to as LUCENT.

     PT. BRIMBUN RAYA INDAH, having its address at Jakarta Barat, as CONSORTIUM
     MEMBER, hereinafter referred to as BRIMBUN.

     PT. LINTAS TEKNOLOGI INDONESIA, having it's address at Tifa Building 3rd
     Floor, Jakarta, as CONSORTIUM MEMBER, hereinafter referred to as LINTAS.

     hereinafter all together in this Amendment referred to as PARTNER.

By first taking into Consideration of the following matters:

a.   whereas, TELKOM and PARTNER has been bound each other in Development
     Contract PSTN Excellence Regional Junction DIVRE II Number:
     PKS.14/HK810/UTA-00/2002 dated 8 February 2002, hereinafter referred to as
     "MAIN CONTRACT".

b.   whereas, TELKOM and PARTNER has changed some articles in the Main Contract
     with the first Amendment Nomor PKS. 155/HK-820/UTA-00/2002 dated August
     22, 2002, hereinafter referred to as "FIRST AMENDMENT";

c.   whereas, TELKOM and PARTNER has changed some articles in the Main Contract
     and first Amendment with the "Second Amendment" Nomor PKS.
     192/HK-820/UTA-00/2002 dated October 25, 2002, hereinafter referred to as
     "SECOND AMENDMENT";

                                       2
<PAGE>
d.   whereas, TELKOM and PARTNER has changed some articles in the Main Contract,
     the first Amendment, and the Second Amendment with the "the Third
     Amendment" Nomor PKS. 121/HK-820/PEM-00/2002 dated December 20, 2002,
     hereinafter referred to as "THIRD AMENDMENT";

e.   whereas, TELKOM and PARTNER has changed some articles in the Main Contract,
     the first Amendment, the Second Amendment and the Third Amendment, with the
     Fourth Amendment Nomor PKS. 21/HK-820/PEM-00/2003 dated 20 March 2003,
     hereinafter referred to as "FOURTH AMENDMENT";

f.   whereas, TELKOM and PARTNER has changed some articles in the Main Contract,
     the first Amendment, the Second Amendment, the Third Amendment, and Fourth
     Amendment with the Fifth Amendment Nomor PKS. 50/HK-820/TCC-00/2003 dated
     26 June 2003 hereinafter referred to as "FIFTH AMENDMENT";

g.   Whereas, MITRA has proposed to change the members of Consortium, and
     TELKOM has approved it with TELKOM's letter no. Tel.667/HK-00/TCC-00/2003
     dated August 11, 2003.

h.   whereas, TELKOM and PARTNER have agreed to amend the Scope of Work of for
     several Rings;

i.   whereas TELKOM with it's Letter number: TEL. 831/LG.270/TCC-00/2003 dated
     OCTOBER 9, 2003 has agreed with Amendment VI;

After having taken into consideration the above matters, TELKOM and PARTNER
have agreed to amend the provisions stipulated in the Main Contract, First
Amendment, Second Amendment, Third Amendment, Fourth Amendment and Fifth
Amendment in accordance with the following terms and conditions:

                                       3
<PAGE>
                                   ARTICLE 1
                                 SCOPE OF WORK

(1)  TELKOM and PARTNER have agreed to amend the Bill of Quantity (BoQ) of the
     scope of work

(2)  Scope of Work based on this Amendment as specified in detail as stated in
     Attachment II of this Amendment.

                                   ARTICLE 2
                                CONTRACT AMOUNT

(1)  The contract price based on this Amendment including VAT, insurance and
     other taxes based on the law of Indonesia as follows:

     -    US$28,791,892.10 (Twenty eight million seven hundred ninety one
          thousand eight hundred ninety two US Dollar and ten cents) and

     -    Rp.122,861,518,120 (One hundred twenty two billion eight hundred sixty
          one million five hundred eighteen thousand one hundred twenty Rupiah)

(2)  The contract price per-ring system an it's breakdown as stated in
     Attachment II of this Amendment.

                                   ARTICLE 3
                         AMENDMENT OF CONSORTIUM MEMBER

(1)  The members of Consortium based on this Amendment consist of:

     a.   PT. Olex Cables Indonesia (Leader)
     b.   Lucent Technologies Singapore Pte Ltd
     c.   PT. Brimbun Raya Indah
     d.   PT. Lintas Teknologi Indonesia

                                       4
<PAGE>
(2)  TELKOM and MITRA agreed that all right, interests, title and obligations of
     PT. LUCENT TECHNOLOGIES INDONESIA under Consortium Agreement had been
     novated to PT. Lintas Teknologi Indonesia and Lucent Technologies Singapore
     Pte Ltd.

                                   ARTICLE 4
                                ACCOUNT CHANGING

TELKOM agreed with MITRA's Bank Account based on this Amendment as follows:

a.   Account No: (USD) 070 0002156268
     Bank Name: Bank Mandiri - Plaza Mandiri Branch, Jakarta
     Account No : (IDR) 102 0102001309
     Bank Name : Bank Mandiri - Sub Jakarta Sudirman, Jakarta
     Under the name of : PT Olex Cables Indonesia

b.   Account No. : (IDR) 060 000001420.001
     Bank Name : PT Bank Negara Indonesia, Tbk
     Dukuh Bawah Branch, Jakarta
     Under the name of : PT Brimbun Raya Indah

c.   Account No. : (USD) 102 0002135801
                 (IDR) 102 0002116249
     Bank name : Bank Mandiri
                Plaza Bapindo Branch, Jakarta
     Under the name of : PT Lintas Teknologi Indonesia

                                   ARTICLE 5
                                   ATTACHMENT

All attachment as follows shall be an unity that could not be separated of this
Amendment, consist of :

Attachment-I:
     Approval letter from TELKOM

Attachment-II :
     Price summary Schedule

                                       5

<PAGE>
Attachment-III:
     Documents of Change of Consortium members

Attachment IV:
     Disburment Plan

Attachment-V:
     Statement of Bank Accounts of Consortium members

Attachment-VI:
     Minutes of Meeting and Clarification

                                   ARTICLE 6
                                     OTHERS

(1)  This Amendment shall be effective as of the date after signing by both
     parties.

(2)  Articles and/or Attachments of the Main Contract and its Amendments which
     are not amended by this Amendment, shall remain prevail and legally binding
     by both parties.

(3)  Copy from this Original Amendment was made in 25 (twenty five) copies by
     PARTNER on PARTNER's own cost for the purpose of supervision of
     implementation and others.

PT. TELEKOMUNIKASI INDONESIA, TBK,          KONSORSIUM
                                            OLEX-LUCENT-BRIMBUN,

[signature]                                 [signature + stamp duty]

TRI DJATMIKO                                FADJAR TJOANDA
----------------------------------          -----------------------------
KEPALA PUSAT CONSTRUCTION CENTER            PIMPINAN KONSORSIUM

                                       6<PAGE>
                                                                    Exhibit 4.29

                             SEVENTH AMENDMENT FOR
                              DEVELOPMENT CONTRACT
                            PSTN EXCELLENCE REGIONAL
                               JUNCTION DIVRE II

--------------------------------------------------------------------------------

                       NUMBER: PKS.101/HK.820/TCC-00/2003
                             DATE: 04 DECEMBER 2003

                                    BETWEEN

                         PERUSAHAAN PERSEROAN (PERSERO)
                        PT TELEKOMUNIKASI INDONESIA, TBK

                                      AND

                         CONSORTIUM OLEX-LUCENT-BRIMBUN

<PAGE>
                               SEVENTH AMENDMENT
                                      FOR
                              DEVELOPMENT CONTRACT
                            PSTN EXCELLENCE REGIONAL
                               JUNCTION DIVRE-II
                                    BETWEEN
                         PERUSAHAAN PERSEROAN (PERSERO)
                       PT. TELEKOMUNIKASI INDONESIA, TBK.
                                      AND
                         CONSORTIUM OLEX-LUCENT-BRIMBUN

--------------------------------------------------------------------------------
                       NUMBER: PKS.101/HK.820/TCC-00/2003

On this day FOURTH of DECEMBER, year TWO THOUSAND THREE, placed at Jakarta,
between the concerned parties:

I.   PERUSAHAAN PERSEROAN (PERSERO) PT. TELEKOMUNIKASI INDONESIA, TBK.,
     telecommunications services and network provider established and
     incorporated under the law of Republic of Indonesia, having its address at
     Jalan Japati No. 1 Bandung 40133, in this legal act represent by, TRI
     DJATMIKO, HEAD OF CONSTRUCTION CENTER, based on the Power of Attorney of
     President Director Number: K.TEL. 107/HK510/UTA-00/02 dated 15 August 2002,
     hereinafter referred to as TELKOM.

II.  CONSORTIUM OLEX - LUCENT - BRIMBUN, a consortium formed under Notarial Deed
     No. 9 dated 14th December 2001, by Notary Benny Djaja, SH, SE, MM., and as
     amended under Notarial Deed No. 20 dated 8th September 2003 by Notary
     Imelda Nur Pane, SH, having its address at Wisma Bisnis Indonesia 15th
     Floor, Jl. Letjen S. Parman Kav. 12, Jakarta-11480; whereas in this legal
     act to be represented by FADJAR TJOANDA, hereinafter referred to as
     PARTNER.

                                  Page 1 of 6
<PAGE>
     CONSORTIUM OLEX - LUCENT - BRIMBUN consists of:

     PT. OLEX CABLES INDONESIA, having its address at Wisma Bisnis Indonesia
     15th Floor, Jakarta, as CONSORTIUM LEADER, hereinafter referred to as OLEX.

     LUCENT TECHNOLOGIES SINGAPORE PTE LTD, having its address at Technopark@
     Chai Chee, 750 D Chai Chee Road, Singapore 469004, as CONSORTIUM MEMBER,
     hereinafter referred to as LUCENT.

     PT. BRIMBUN RAYA INDAH, having its address at Pos Pengumben 10A, Jakarta
     Barat, as CONSORTIUM MEMBER, hereinafter referred to as BRIMBUN.

     PT. LINTAS TEKNOLOGI INDONESIA, having it's address at Tifa Building 3rd
     Floor, Jakarta, as CONSORTIUM MEMBER, hereinafter referred to as LINTAS.

     hereinafter all together in this Amendment referred to as PARTNER.

By first taking into Consideration of the following matters :

a.   whereas, TELKOM and PARTNER has been bound each other in Development
     Contract PSTN Excellence Regional Junction DIVRE II Number :
     PKS.14/HK810/UTA-00/2002 dated 8 February 2002, hereinafter referred to as
     "MAIN CONTRACT".

b.   whereas, TELKOM and PARTNER has changed some articles in the Main Contract
     with the first Amendment Nomor PKS. 155/HK-820/UTA-00/2002 dated August
     22, 2002, hereinafter referred to as "FIRST AMENDMENT";

                                  Page 2 of 6
<PAGE>
c.   whereas, TELKOM and PARTNER has changed some articles in the Main Contract
     and first Amendment with the "Second Amendment" Nomor PKS.
     192/HK-820/UTA-00/2002 dated October 25, 2002, hereinafter referred to as
     "SECOND AMENDMENT";

d.   whereas, TELKOM and PARTNER has changed some articles in the Main Contract,
     the first Amendment, and the Second Amendment with the "the Third
     Amendment" Nomor PKS. 121/HK-820/PEM-00/2002 dated December 20, 2002,
     hereinafter referred to as "THIRD AMENDMENT";

e.   whereas, TELKOM and PARTNER has changed some articles in the Main Contract,
     the first Amendment, the Second Amendment and the Third Amendment, with the
     Fourth Amendment Nomor PKS. 21/HK-820/PEM-00/2003 dated 20 March 2003,
     hereinafter referred to as "FOURTH AMENDMENT".

f.   whereas, TELKOM and PARTNER has changed some articles in the Main Contract,
     the first Amendment, the Second Amendment, the Third Amendment, and Fourth
     Amendment with the Fifth Amendment Nomor PKS. 50/HK-820/TCC-00/2003 dated
     26 June 2003 hereinafter referred to as "FIFTH AMENDMENT".

g.   whereas, TELKOM and PARTNER has changed some articles in the Main
     Contract, the first Amendment, the Second Amendment, the Third Amendment,
     Fourth Amendment and Fifth Amendment with the Sixth Amendment Nomor PKS.
     87/HK-820/TCC-00/2003 dated 09 October 2003 hereinafter referred to as
     "SIXTH AMENDMENT".

h.   whereas, PARTNER has completed and handed-over some Ring-system e.l Ring
     X, Ring Y, Accelerate Ring Y, Ring 1, Ring 2, Ring 3, Ring 4, Ring 5, Ring
     7, Ring 8, Ring 10, Ring 11, NMS, Spare, Supporting Facility, SDH and DXC
     Training which copy of BAST-I attached.

                                  Page 3 of 6
<PAGE>
i.   whereas, TELKOM and PARTNER have agreed to amend the Scope of Work and
     Implementation Schedule of several Rings;

j.   whereas TELKOM with it's Letter number: TEL:937/LG270/TCC-00/2003 dated
     DECEMBER 2, 2003 has agreed with Amendment VII;

After having taken into consideration the above matters, TELKOM and PARTNER have
agreed to amend the provisions stipulated in the Main Contract, First
Amendment, Second Amendment, Third Amendment, Fourth Amendment, Fifth Amendment
and Sixth Amendment in accordance with the following terms and conditions:

                                   ARTICLE 1
                                 SCOPE OF WORK

(1)  TELKOM and PARTNER have agreed to amend the Bill of Quantity (BoQ) of the
     scope of work.

(2)  Scope of Work based on this Amendment as specified in detail as stated in
     Attachment II of this Amendment.

                                   ARTICLE 2
                                CONTRACT AMOUNT

(1)  The contract price based on this Amendment including VAT, insurance and
     other taxes based on the law of Indonesia as follows:

     - US$ 28,880,957.30 (TWENTY EIGHT MILLION EIGHT HUNDRED EIGHTY THOUSAND
       NINE HUNDRED FIFTY SEVEN UNITED STATES DOLLAR AND THIRTY CENTS) and

                                  Page 4 of 6
<PAGE>
     *    RP. 123.239.741.460,00 (ONE HUNDRED TWENTY THREE BILLION TWO HUNDRED
          THIRTY NINE MILLION SEVEN HUNDRED FORTY ONE THOUSAND FOUR HUNDRED
          SIXTY RUPIAH)

(2)  The contract price per-ring system and it's breakdown as stated in
     Attachment II of this Amendment.

                                   ARTICLE 3
                             IMPLEMENTATION PERIOD

TELKOM and PARTNER agree to amend the Implementation Schedule for some Rings.
The Implementation Schedule of each Ring as stated in Attachment III of this
Amendment.

                                   ARTICLE 4
                                   ATTACHMENT

All attachment as follows shall be an unity that could not be separated of this
Amendment, consist of:

Attachment-I:
     Approval letter from TELKOM

Attachment-II:
     BoQ and Price Schedule

Attachment-III:
     Project Implementation Schedule

Attachment IV:
     Disburment Plan

Attachment-V:
     Minutes of Meeting and Clarification

Attachment-VI:
     Copy of BAST-I

                                  Page 5 of 6
<PAGE>
                                   ARTICLE 5
                                     OTHERS

(1)   This Amendment shall be effective as of the date after signing by both
      parties.

(2)   Articles and/or Attachments of the Main Contract and its Amendments which
      are not amended by this Amendment, shall remain prevail and legally
      binding by both parties.

(3)   Copy from this Original Amendment was made in 25 (twenty five) copies by
      PARTNER on PARTNER's own cost for the purpose of supervision of
      implementation and others.

PT. TELEKOMUNIKASI INDONESIA, TBK.           KONSORSIUM
                                             OLEX-LUCENT-BRIMBUN,

[signature]                                  [signature + stamp duty]

TRI DJATMIKO                                 FADJAR TJOANDA
-------------------                          -------------------
KEPALA PUSAT CONSTRUCTION CENTER             PIMPINAN KONSORSIUM

                                  Page 6 of 6

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