The head of the UN-backed humanitarian taskforce for Syria, Jan Egeland, told reporters that aid agencies were ready to send life-saving supplies to the city's rebel-held eastern districts but raging violence has blocked convoys from deploying.
"Humanitarian convoys are ready, humanitarian workers are ready. We have the supplies. We need a break in the fighting," Egeland said following the weekly meeting of the taskforce co-chaired by Russia, which supports Damascus, and the United States, which backs some rebel groups.
Egeland urged both powers to pressure their allies to "give us 48 hours every week to be able to go to eastern Aleppo".
"The clock is ticking," he said, describing people in Syria's second city as being "on the brink of starvation".
Access to eastern Aleppo was completely cut off on July 7 when Syrian President Bashar al-Assad's forces took control of the Castello Road, the last supply route.
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The head of the International Committee of the Red Cross's Syria mission, Marianne Gasser, who has been in Aleppo for a week, said "the bombing is constant".
"No child, let alone adult, should have to live through this," she said in a statement. "People are trying to survive in the most desperate of circumstances."
The UN has identified 18 areas in Syria as besieged, mostly by government forces.
Egeland said only three of those areas have received aid this month.
In Madaya, a besieged area in the southwest where dozens starved to death late last year, supplies are believed to have run out, with no humanitarian deliveries since April 30.
"The mothers have no food anymore to give to the children in Madaya," Egeland said.
The crisis in Syria began with anti-government protests in March 2011 before exploding into a civil war that has killed more than 280,000 people.
