Washington: The United States is increasing pressure on Sri Lanka to investigate the deaths of thousands of civilians at the end of its civil war.
Rights groups feel a Sri Lankan government investigation is not doing its job.
The Senate passed a resolution this week urging an international probe into war crimes allegations. The State Department is likely to follow suit.
The quarter-century-long conflict came to a bloody conclusion in 2009 when government forces cornered the last Tamil Tiger rebels on a sliver of land in the north-east of the island.
About 300,000 Tamil civilians were caught in the battle, with Amnesty International saying between 7,000 and 40,000 were killed.
Colombo appointed a Lessons Learned and Reconciliation Commission last year, which has taken evidence from ethnic minority Tamils, government officials, politicians, civil and religious leaders and former rebels.
International rights groups have refused to testify before it, saying the commission is pro-government and has no mandate to investigate the killings.
Robert Blake, the US assistant secretary of state for South and Central Asia, said the US wanted to see a proper investigation.
Accountability
"If they (the commission) are not willing to take the accountability issue seriously, then there will be pressure from the international community to look at some kind of international option," said Blake, who was US ambassador to Sri Lanka at the war's end.
According to a diplomatic cable published by WikiLeaks, Blake's successor as ambassador, Patricia Butenis, felt there was little hope of a proper investigation because responsibility for many of the alleged crimes is thought to rest with senior civilian and military leaders, including President Mahinda Rajapaksa.
