The UN is trying to get an advance force of peacekeepers into Lebanon in 10-15 days, a senior official has said.
The UN force will boost the existing team of peacekeepers
The force would be up to 3,500-strong, to be boosted later to the full 15,000 agreed in the UN ceasefire resolution.
Lebanon says it will start moving its own 15,000-strong force towards the south this week, while Israel says it could pull out within 10 days.
The moves come as a two-day ceasefire between Israel and Hezbollah continues to hold, despite sporadic violence.
Meanwhile, thousands of refugees have been returning to south Lebanon, despite Israeli warnings that it is not yet safe to do so.
Aid agencies are trying to deliver badly-needed food and medicine to the area, while the UN has warned returnees of a further danger from unexploded ordnance.
Fears of delay
The advance party of peacekeepers will join an existing UN force that was already in place when the crisis erupted in July but had no mandate to intervene.
IMPACT: 34 DAYS OF FIGHTING
About 1,000 - mostly civilians
No precise data on Hezbollah dead
Soldiers: 114 (IDF)
Civilians: 43 (IDF)
700,000 - 900,000 (UNHCR; Lebanese govt)
500,000 (Human Rights Watch)
Senior officials say the initial deployment will consist of soldiers, mostly from France, but that it is hoped troops from Islamic countries will join them later.
The plan is for the UN peacekeepers to take over as Israel starts pulling out from the south, and eventually to hand over to Lebanese forces.
But UN officials acknowledge there are as yet no firm pledges of troops from any countries, despite American calls for a rapid deployment.
BBC diplomatic correspondent Bridget Kendall, at the UN in New York, says there is clearly concern at the apparent reluctance by so many countries to sign up.
The fear is, if there is further delay, it could put pressure on an already fragile ceasefire and increase the risks of the whole operation, our correspondent says.
French Foreign Minister Philippe Douste-Blazy is expected to meet Lebanese Prime Minister Fouad Siniora in Lebanon on Wednesday to discuss conditions for the deployment of French troops.
In Beirut, Lebanese Defence Minister Elias Murr said the army would be ready within days to start moving to the area of the Litani River in the south.
He said it was not the job of the Lebanese army to disarm Hezbollah fighters, but he was confident they would withdraw from southern areas as the troops moved in.
In a separate development, the Israeli Army said it had killed a senior Hezbollah commander moments before the ceasefire went into effect on Monday.
The dead man was named as Sajed Dawayer, but no details were given about how or where he died. There was no immediate comment from Lebanon.
Israel said it had shot dead three Hezbollah fighters on Tuesday, and injured two others as sporadic post-truce violence continued.
Earlier, Israeli politicians dismissed claims by the leaders of Iran and Syria - long-term backers of Hezbollah - that the fighting in Lebanon had resulted in a victory for Hezbollah.
In Damascus, President Bashar al-Assad said Israel had been defeated and Hezbollah had "hoisted the banner of victory".
The defiant speech was a clear sign of how US opponents in the Middle East have been emboldened by the outcome of the conflict, says the BBC's Jon Leyne in Damascus.
In Iran, President Mahmoud Ahmadinejad said Hezbollah had foiled plans to forge a Middle East dominated by "the US, Britain and Zionists".
"On one side, it's corrupt powers.... with modern bombs and planes. And on the other side is a group of pious youth relying on God," he said.
Israeli Foreign Minister Tzipi Livni, rejecting the claims of a Hezbollah victory, said she would not be provoked by Syria or Iran.
She warned that if Israel was threatened it would take any action necessary to defend itself, just as it had done over the last few weeks.
Ms Livni will hold talks with the UN Secretary General Kofi Annan on Wednesday about how to implement the ceasefire in full.
Israeli Defence Minister Amir Peretz called for dialogue with Lebanon, and said Israel should also prepare conditions for talks with Syria.