Diplomats at the United Nations are discussing possible changes to a draft resolution aimed at ending the fighting between Israel and Hezbollah.
A building collapsed after air strikes on south Beirut
An Arab League delegation is travelling to New York to push Lebanon's demands for the text to call for an immediate withdrawal of Israeli forces.
Lebanon has pledged 15,000 troops for the border area when Israel pulls out.
Israel continued air strikes overnight after at least 49 people died in raids on Lebanon on Monday.
The current text - drafted by the US and France - calls for an immediate cessation of hostilities and lays the groundwork for a second resolution that would install an international peacekeeping force in southern Lebanon.
But the Lebanese government wants changes which include a requirement that Israel withdraw all its forces as soon as there is a cessation of hostilities - rather than waiting for the eventual deployment of a multi-national force.
The talks came as UN Secretary-General Kofi Annan issued a new report criticising both sides for targeting civilians during the fighting.
Mr Annan said the Israeli bombing of the village of Qana on 30 July could be part of "a pattern of violations of international law".
He called for a further investigation into the Qana attack, which killed at least 28 people, according to Human Rights Watch - although initially the toll was put at 56.
Israel says it carried out about 80 air strikes across Lebanon on Monday night, targeting what it said were Hezbollah buildings and rocket launchers.
On Monday, Israeli air strikes on Lebanon were met by the militant group Hezbollah with a barrage of more than 100 rockets, wounding some Israeli civilians.
Rescuers in Beirut said at least 15 people had been killed in evening air strikes on a southern suburb that caused a building to collapse.
The Israeli army warned southern Lebanese residents to stay indoors from 2200 (1900 GMT) on Monday.
Three Israeli soldiers were killed in clashes in the southern Lebanese village of Bint Jbeil, the Israeli military said, adding that five Hezbollah militants were also killed.
The Israeli military said it had downed an Hezbollah drone - the first time an unmanned spotter plane has been destroyed in the conflict.
Mr Olmert told reservists Israel was "not stopping" its offensive
The Israeli army also released video footage that purported to show a Hezbollah fighter confessing to taking part in the 12 July raid in which two Israeli soldiers were captured, triggering the conflict.
Lebanese Prime Minister Fouad Siniora drastically revised down the death toll of an Israeli air strike in the village of Houla, where he initially said 40 people had died when a building collapsed on them.
A UN spokesman later said five people had died in the attack.
Correspondents say the UN Security Council will vote, at the very earliest, on the draft resolution on Tuesday.
Both the US and France have said they will listen to the Arab delegation's concerns.
But US President George W Bush, at his ranch in Texas, warned against creating "a vacuum into which Hezbollah and its sponsors are able to move more weapons".
The BBC's diplomatic correspondent says the US and France will be reluctant to see the vote delayed very long for fear that the whole plan could collapse.
Senior Israeli officials have said they are broadly happy with the text of the UN resolution.
More than 900 Lebanese, most of them civilians, have been killed in the conflict, the Lebanese government said. More than 90 Israelis, most of them soldiers, have also been killed.
Israeli Defence Minster Amir Peretz said Israel would step up its offensive against Hezbollah rocket-launching sites if the diplomatic process does not reach a successful conclusion.
And Prime Minister Ehud Olmert, according to his office, told reservists on a visit to the Lebanese border: "I give to you all the power and the backing. We are not stopping."