The UN has called for a three-day truce between Israel and Hezbollah to allow for aid to enter southern Lebanon and for casualties to be removed.
The UN wants the injured to be evacuated during a truce
UN humanitarian chief Jan Egeland said children, elderly and disabled had been left stranded by two weeks of fighting.
US President George W Bush has again dismissed calls for an immediate truce, arguing instead for an international force to be deployed in Lebanon.
US Secretary of State Condoleezza Rice returns to the region on Saturday.
President Bush said he would "work with the leaders of Israel and Lebanon to seize this opportunity to achieve lasting peace and stability for both of their countries".
Ms Rice is expected to lobby for a UN Security Council resolution that would lead to an international force being deployed in southern Lebanon.
UK Prime Minister Tony Blair, who met Mr Bush in Washington on Friday, said world leaders would discuss the deployment of a "stabilisation force" in Lebanon at a meeting at the UN headquarters in New York on Monday.
UN Secretary General Kofi Annan said countries who may be in a position to contribute troops to an international force would attend Monday's meeting.
"Obviously it will be preliminary discussions because we do not have the mandate of the Security Council yet," Mr Annan said.
The UN Security Council is due to discuss the issue later next week.
Mr Bush said the US and UK will push for a "Chapter Seven resolution setting out a clear framework for cessation of hostilities on an urgent basis and mandating the multinational force".
UN 'not impotent'
Briefing the Security Council on Friday, Mr Egeland said some 600 people had been killed by Israeli action in Lebanon, of which around a third were children.
"It's been horrific... There is something fundamentally wrong with the war, where there are more dead children than armed men," Mr Egeland said.
He said he would ask the parties involved in the conflict "for at least a 72-hour start of this cessation of hostilities so that we can evacuate the wounded, children, the elderly, the disabled from the crossfire in southern Lebanon".
He said existing humanitarian corridors were not adequate to meet the immense needs of people in the war zone.
Mr Egeland was speaking after completing a visit to Lebanon, Israel and the Gaza Strip.
The UN's Deputy Secretary General has denied the world body feels powerless after the loss of four peacekeepers to Israeli fire in Lebanon this week.
Mark Malloch-Brown told the BBC the UN felt "concerned and frustrated, but not impotent".
The UN Security Council issued a statement on Thursday voicing "shock and distress" at the deaths, after the US blocked calls for harsher criticism of Israel.
Israeli army chief Dan Halutz said Israel has killed 26 Hezbollah fighters in Bint Jbeil in southern Lebanon, inflicting "enormous" damage on the Shia militia.
A convoy carrying a TV crew and refugees was hit on Friday
Ten civilians, including a Jordanian, also reportedly died in Israeli attacks in south Lebanon on Friday.
Earlier, Hezbollah said it had fired a new long-range rocket, called the Khaibar-1, into northern Israel.
Also on Friday, two mortar rounds hit a convoy of vehicles evacuating civilians from the village of Rmeish, close to the Israeli border. Two people travelling in a German TV car were wounded.
Refugees from Rmeish said conditions were deteriorating rapidly in the area.
They said some of those still trapped in the village were drinking water from a stagnant pond.
A senior official at the UN refugee agency (UNHCR) in Lebanon told the BBC that supplies were "running out very, very fast" in southern Lebanon.
"The south is definitely where the critical needs are at the moment. You've got active combat going on, several tens if not hundreds of thousands of persons displaced within the south," Arafat Jamal said.
Aid agencies also said that many people in the area were in urgent need of medical treatment.