JAKARTA, Indonesia (AP) -- The United Nations said it will boycott a truth commission looking into hundreds of killings during East Timor's violent break from Indonesia in 1999 unless the panel scraps the possibility of granting amnesty to human rights violators.

The world body "cannot endorse or condone amnesties for genocide, crimes against humanity, war crimes or gross violations of human rights, nor should it do anything that might foster them," the U.N. said in a statement Thursday.

U.N. and Timorese investigators named scores of alleged perpetrators of rapes, murders and plunder during several months of bloodshed, including many high ranking Indonesian military officials, but none of their cases have ever gone to court.

If the panel's mandate in not altered to meet international standards, U.N. officials will "not testify at its proceedings or take any other steps that would support the work" of the commission, U.N. spokeswoman Marie Okabe was quoted as saying.

Commission Chairman Benyamin Mangkudilaga said Friday in an interview no decision had been made about granting amnesty, but did not rule out the possibility.

He criticized the U.N. for failing to appear before the commission to clarify its role in the violence, saying "if they do not come, then their credibility is at stake."

The Commission of Truth and Friendship, established by Indonesia and East Timor in 2005 to improve bilateral relations, has no power to prosecute individuals or order anyone to testify. It has taken voluntary statements from dozens of witnesses.

The decision could have serious consequences for the commission, which had been counting on the U.N. to provide accounts of events and documentation of its East Timor mission. The decision not to cooperate with the commission could hurt its credibility.

East Timor voted overwhelmingly to end nearly a quarter century of Indonesian rule in a U.N.-sponsored public referendum eight years ago that triggered a burst of killing, looting and burning by vengeful Indonesian soldiers and their military proxies.

Only one militia leader has been punished in Indonesia for the violence that left up to 1,500 dead and devastated as much as 70 percent of the tiny nation's infrastructure in a scorched earth campaign.

Political leaders appear reluctant to press for trials that could upset diplomatic relations, despite calls by human rights groups for criminal proceedings.

East Timor President Jose Ramos-Horta, a Nobel Peace prize winner, recently hailed the commission as an example for post-conflict reconciliation, but critics dismiss it as a whitewash of Indonesia's role in crimes.

East Timor, a former Portuguese colony, descended into chaos last year when fighting between rival police and army factions morphed into widespread gang warfare, looting and arson. At least 37 people were killed and 155,000 fled their homes.