UN chief Ban Ki-moon was due to land in Sri Lanka later on Friday on a 24-hour mission to press its government for unfettered humanitarian access to an estimated 250,000 civilians displaced by conflict.
The secretary general was expected in the evening ahead of talks on Saturday with President Mahinda Rajapakse and Foreign Minister Rohitha Bogollagama.
It follows the routing of the Tamil Tiger rebels -- and the death of their leader Velupillai Prabhakaran -- that ended a bitter 26-year insurgency for a Tamil homeland.
"Tonight, I leave for Sri Lanka. You have all watched what is happening," the UN head told students at a Johns Hopkins University commencement ceremony in Washington before leaving the United States.
"You all empathize with the plight of people trapped by fighting and living in terror and grave hardship."
Ban was also to tour the northern conflict zone and the adjacent sprawling Menik Farm emergency shelter for internally displaced persons in Vavuniya.
Menik Farm is home to more than 130,000 civilians displaced by the fighting between government forces and the separatist Liberation Tigers of Tamil Eelam (LTTE), according to UN officials.
The high-profile visit comes as UN and relief aid agencies complain about restrictions placed by Colombo authorities on vehicle access to such camps.
International aid group Oxfam urged the Sri Lankan government on Thursday to ease restrictions on access to camps, warning that a ban on aid vehicles was putting thousands of lives at risk.
The International Committee of the Red Cross and UN agencies also protested about "curtailed" access, including to Menik Farm, after restrictions imposed last weekend.
The 20-plus reporters travelling with the UN secretary general, including AFP, are to get a rare glimpse at Menik Farm and the conflict zone.
In announcing his visit in Geneva earlier this week, Ban said that he was relieved by the conclusion of military operations "but deeply troubled by the loss of civilian lives."
The Sri Lankan government announced Monday that it had wiped out the LTTE leadership and retaken the final patch of territory from the rebels who ran a de facto state in the Indian Ocean island's northeast only two years ago.
The conflict has cost up to 100,000 lives, according to UN estimates. The world body says the government's offensive against the rebels has claimed more than 7,000 civilian lives since the start of the year.
Ban has also made it clear that he wants to see swift progress not only on immediate humanitarian aid and reconstruction, but also on reconciliation with the disenfranchised Tamil minority, which make up 12.6 per cent of Sri Lanka's population of 20 million.
"Progress on all three fronts must be in parallel, and it must begin now," Ban said on Tuesday, adding that any serious allegations of war crimes "should be properly investigated."
US Secretary of State Hillary Clinton conveyed a similar message in a phone call Thursday to Rajapakse, according to a State Department official.
Also Thursday, Rajapakse appealed for an end to the ethnic divisions in Sri Lanka, which has a Sinhalese majority, saying the Tigers' defeat should usher in an era of unity.
"I see it as the duty of all to ensure that all differences that hitherto divided our people are subsumed in the great and momentous joy that is shared by us all," he said in a statement.
Ban is scheduled to give a news conference before departing for Copenhagen late on Saturday.