The nominee to be the next US ambassador to Sri Lanka Michele Sison says human rights will be at the top of her agenda.

Sison said on Wednesday that serious allegations of violation of international human rights law committed during the island nation's civil war have yet to be investigated and have slowed reconciliation.

"One cannot have true reconciliation, general reconciliation, without that accountability," Sison told her Senate confirmation hearing.

A UN report found that thousands died and that Sri Lankan troops deliberately targeted civilians. It said Tamil rebels used civilians as human shields.

Democrat Senator Robert Casey urged an independent investigation into alleged war crimes, saying the issue would not go away "until the world sees results”.

He said Sri Lanka has yet to implement recommendations made six months ago by its own reconciliation commission, and cited figures from the Switzerland-based Internal Displacement Monitoring Centre, that nearly 100,000 Tamils are still displaced. He said the military presence in the island's north and east was obstructing their resettlement.

Sison said the US was looking for "near term progress" by Sri Lanka, particularly in setting a date for provincial elections in the country's north and demilitarisation of former conflict zones.

Human rights issues, including protection of civil society and a free media, "will be on the top of my agenda”, she said.

Sison also said that if confirmed, she would be a vigorous advocate for US commercial interests in Sri Lanka.(PTI)