A United States diplomat arrived in Sri Lanka on Monday to discuss issues relating to alleged war crimes stemming from the Indian ocean island nation’s quarter-century civil war which ended four years ago.

Stephen J. Rapp, an ambassador-at-large in the Office of Global Criminal Justice, will be in Sri Lanka until Saturday to meet government officials, and political and civil society leaders to discuss issues focusing on Sri Lanka’s justice, accountability and reconciliation processes, the U.S. state department said.

His visit comes two months ahead of a United Nations Human Rights Council review of Sri Lanka’s progress in probing alleged war crimes. The U.S. has successfully carried two resolutions at the United Nations Human Rights Council urging Sri Lanka to initiate a credible investigation.

U.N. rights chief Navi Pillay has said she would recommend that the council establish its own probe if Sri Lanka fails to show progress by March.

Western nations have been pressing Sri Lanka to account for thousands of civilians who are suspected of being killed in the final months of the quarter- century war that ended in May, 2009 when the government forces crushed the Tamil Tiger rebels who were fighting for a homeland for ethnic minority Tamils.

According to a U.N. report, as many as 40,000 civilians may have died in the last few months of the fighting, which the government disputes.

For two years after the war, Sri Lanka’s government insisted that not a single civilian was killed. But later in 2011 it acknowledged some civilian deaths and announced a census of the war dead but its results were vague.

Government troops were accused of deliberately shelling civilians, hospitals and blocking food and medical aid to hundreds of thousands of people boxed inside a tiny strip of land as the rebels mounted their last stand. The government denies the charges.

The rebels were accused of holding civilians as human shields, killing those who escaped their control and recruiting child soldiers.