The United Nations has sent its top humanitarian official to Sri Lanka to secure the safety of up to 50,000 civilians trapped in fighting between government forces and Tamil Tiger rebels.
The Under-Secretary General for Humanitarian Affairs John Holmes arrived late on Saturday as the White House called for an immediate ceasefire and the Group of Eight industrialised nations made a strong statement.
"The top priority remains the preservation of the lives of the tens of thousands of civilians still trapped inside the combat zone," Mr Holmes said in a statement.
He is due to leave on Monday after visiting internally displaced people and holding talks with Sri Lankan leaders, including President Mahinda Rajapakse.
The United Nations believes up to 50,000 non-combatants are still trapped in the sliver of jungle where the Sri Lankan military has surrounded the remnants of the once powerful Liberation Tigers of Tamil Eelam (LTTE) army.
Around 100,000 civilians have already managed to escape the area, and Mr Holmes said he also wants to inspect the government-run camps where critics say the refugees are being held in prison-like conditions.
The plight and suffering of those caught in the fighting prompted US President Barack Obama's administration on Friday to urge an end to hostilities.
"We call on both sides to stop fighting immediately and allow civilians to safely leave the combat zone," the White House said in a statement.
The Sri Lankan government has so far resisted all calls to halt an offensive that is now on the brink of wiping out the LTTE who have been fighting for an independent Tamil homeland since 1972.