The president's office has said the panel will also make recommendations on how to ensure the country does not return to conflict.
Independent inquiry call
Around 7,000 Tamil civilians were killed in the final stages of the civil war last year, according to a United Nations report.
Colombo, however, has rejected the UN report, and refused to allow any independent body to investigate war crimes allegations.
US legislators have called for an independent international inquiry into possible war crimes, arguing that the panels set up by the Colombo-based government "lacked the needed credibility".
"There is mounting evidence that suggests both parties in the conflict committed severe human rights violations during the conflict," US congressmen said in a letter addressed to Hillary Clinton, the US secretary of state.
"We urge you to call for a robust and independent international investigation that would finally clarify the events that occurred during the conflict and provide the foundation for a sustainable peace in Sri Lanka."