The UN has warned it will boycott a truth commission examining violence in East Timor unless it rules out recommending amnesties for rights crimes.
East Timor and Indonesia set up the Commission of Truth and Friendship (CTF) in 2005 to probe the unrest surrounding East Timor's vote for independence in 1999.
Indonesia ruled the former Portuguese colony for 24 years, and its military is accused of backing militias that instigated violence leaving 1,400 people dead.
"The organisation 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," Secretary-General Ban Ki-moon's spokeswoman said in a statement on the UN's website dated on Thursday.
The commission, which is set up along the lines of South Africa's post-apartheid Truth and Reconciliation Commission, has heard testimony from dozens of witnesses.
Spokeswoman Marie Okabe said the CTF had invited former staff members of the UN Mission in East Timor to testify at its proceedings.
But the CTF's terms of reference do not preclude it from recommending amnesties, she said.
"Unless the terms of reference are revised to comply with international standards, officials of the United Nations will, therefore, not testify at its proceedings or take any other steps that would support the work of the CTF and thereby further the possible grant of amnesties in respect of such acts," she said.
East Timor voted overwhelmingly in favour of breaking away from Indonesia in a UN-backed referendum, but the vote triggered an orgy of violence that also saw much of the nation's infrastructure deliberately destroyed.
East Timor's leaders have taken a largely conciliatory stance towards Indonesia since then, arguing that good relations with its giant and more powerful neighbour are crucial to its future.