The United Nations said an operation to allow civilians to leave besieged districts of the Syrian city of Homs will be extended until Wednesday night.
The announcement on Monday was welcomed by UN humanitarian chief Valerie Amos, and follows a successful but difficult three-day evacuation mission in Homs, where gunfire and attacks have frustrated progress.
"I hope this will allow us to evacuate yet more civilians and deliver much needed additional supplies," said Amos in a statement which reported that more than 800 people have been helped out of Homs since late Friday.
"The protection of civilians caught up in this horrendous conflict in Syria is the greatest priority for UN agencies and humanitarian partners," Amos added.
The civilians who have managed to leave are among an estimated 3,000 people trapped since June 2012 in parts of the old city held by rebels and under attack by troops from President Bashar al-Assad's regime. The Syrian army have staged a string of huge offensives, with near-daily bombardments killing thousands.
The humanitarian exit operation is part of a deal brokered by the United Nations between the regime and the Syrian opposition after months of negotiations.
But a ceasefire permitting the Homs evacuation proved fragile Saturday, with the first aid convoy coming under attack and mortar shells hitting a rebel-held district on Sunday, killing five people.
Activists have blamed pro-regime factions in neighborhoods bordering the besieged districts for the attacks, while Syrian state television said "armed terrorist groups" had fired during the UN operation.
Meanwhile, UN diplomats in New York have resumed the task of trying to persuade Russia to back a new humanitarian resolution.
A draft text of the non-binding resolution, seen by AFP, prepared by Australia, Jordan and Luxembourg "demands that all parties, in particular the Syrian authorities, immediately end the sieges of the Old City of Homs," as well as in Aleppo, Damascus and other cities.
Such steps are needed "to allow the delivery of humanitarian assistance, including medical assistance," it said.
Monday's meeting included permanent Security Council members Britain, the United States and France.
However, Russia's envoy to the United Nations, Vitaly Churkin, did not attend, nor did China's representative.
Churkin last week rebuffed efforts at the United Nations for a humanitarian resolution, saying it "is not a good time" for any such plan in the Security Council and citing concern that it would "be an effort to politicize," the Syrian conflict.