Sri Lanka’s main opposition party has demanded the government conduct a domestic investigation into war crimes allegations arising from the quarter-century civil war. It says the government’s long inaction has placed the nation “on a razor’s edge of devastating international action.”

The statement Thursday from the United National party offered its support for such an inquiry.

Both the Sri Lankan government and the defeated Tamil Tiger rebels have been accused of serious human right violations, mainly in the final months of the war that ended in 2009.

The United States has said it will sponsor a third resolution in the U.N. Human Rights Council in March because Sri Lanka has not shown sufficient progress in ensuring justice and accountability as recommended by a local war commission.