The United Nations is urging the Sri Lankan government and Tamil Tiger rebels to temporarily stop fighting in order to allow civilians trapped in the conflict zone to safely leave.

United Nations humanitarian chief John Holmes says there may be between 150,000 and 190,000 civilians still trapped in the Vani area of northern Sri Lanka, the last stronghold of Liberation Tigers of Tamil Eelam or the LTTE. He urged both sides to call a brief cease-fire to let them leave.

"Therefore, our first appeal is to the LTTE to let the civilians out in a safe and orderly fashion. And I very much hope they will do that. We are also concerned that the government of Sri Lanka should do everything they can to avoid civilian casualties, to do as they said they will do and not to use heavy weapons in this area, and we also call them to respect international humanitarian law in every area," he said.

Speaking after an informal briefing to Security Council members, Holmes told reporters the U.N. is pressing for better humanitarian access to this area, which comprises about 21 square kilometers of jungle and beach on the northeastern coast.

"We are pressing for more aid to be able to get into this particular zone, so we can get the necessary food, medical supplies and other things people need there and to have humanitarian access to the area. And we have suggested again some kind of humanitarian pause to allow that to happen and to allow the civilian population to leave," he said.

Sri Lanka's U.N. Ambassador [H.M.G.S. Palihakkara] said his government would be willing to agree to a 48-hour "no-fire" period to help evacuate civilians. 

"The issue is not the pause, the issue is if the LTTE is ready to let these people go - at least part of them go. I would persuade my government to agree to a modality to facilitate that," he said.

He denied human rights groups charges that the Sri Lankan military has indiscriminately shelled the so-called "no-fire zone" where tens of thousands of civilians are trapped by the Tamil rebels, saying only that there may have been "one or two occasions where return fire" from the military may have caused casualties.

U.S. envoy Rosemary DiCarlo said the United States is deeply concerned about the deteriorating humanitarian situation and the civilians caught in the conflict zone. Ambassador DiCarlo said the United States wants to see the Sri Lankan government come forward with an initiative that allows Tamil citizens who renounce violence to have a viable role in the society. She said that would make a big difference in final resolution of this problem.

The Sri Lankan military has been fighting the rebels since 1983 and says it is close to capturing their last strip of territory.