Talking tough, the United States on Friday told Sri Lanka [Images] and the Liberation Tigers of Tamil Eelam to immediately end the war in the island's north and cautioned Colombo that its unity and reconciliation could be at stake if it continued with its current endeavours to end the ethnic conflict 'militarily'.

The White House, in its first statement on the Sri Lankan conflict after President Barack Obama [Images] assumed office on January 20, said it was taking 'very seriously' the allegations of violations of international humanitarian law by both sides.

"Further continuation of the present situation would compound the tragedy as the military end of the conflict only breeds further enmity and ends hopes for reconciliation and a unified Sri Lanka in the future," the White House said.

It said the US is deeply concerned about the plight of innocent civilians caught up in the conflict between the government of Sri Lanka and the Tamil Tigers, who are confined to a 10 sq km swathe of coastal land in Mullaitivu in Wanni region, and the mounting death toll. "We call on both sides to stop fighting immediately and allow civilians to safely leave the combat zone," it said.

The White House asked Sri Lanka to stop shelling the 'safe zone' and asked it to allow international aid groups and media from accessing civilians who have managed to escape from the clutches of the LTTE [Images].

"International aid workers should have access to all sites where internally displaced persons are being registered and sheltered," the statement said.

The US is working with international partners to attempt to care for those civilians who can be reached, it said. Sri Lanka says it is close to defeating the Tamil Tigers, who have been fighting for a separate Tamil homeland on the island since late 1970s. The government has designated an area as a safe zone and says tens of thousands of civilians have escaped.

But it also says top LTTE leaders, including its chief Velupillai Prabhakaran, are hiding among the civilians. The government has rejected appeals to end the war and has also turned down requests to send humanitarian teams into the area.