Sri Lanka's main opposition presidential candidate says the country cannot be charged with war crimes in the International Criminal Court, but he will launch a domestic inquiry if he wins a January election.

Maithripala Sirisena said in a policy statement on Friday that Sri Lanka has not ratified the statute that established the international court, and that he would therefore institute an investigation by a local independent court.

The U.N. Human Rights Council is investigating allegations of war crimes committed by the Sri Lankan government and Tamil Tiger rebels during the country's civil war. An earlier U.N. inquiry said at least 40,000 ethnic Tamil civilians died in the final months of the war, which ended in 2009.

Sirisena is challenging President Mahinda Rajapaksa for the presidency.