The Syrian government has effectively stopped aid convoys this month and the besieged city of Aleppo is close to running out of fuel, making U.S.-Russian peace talks in Geneva on Friday even more urgent, the United Nations said. "Convoys are not rolling at the moment in Syria," the U.N. humanitarian chief told reporters in Geneva, although an air bridge to the Kurdish-controlled northeastern city of Hasaka has continued operating, and there have been a handful of evacuations from the besieged towns of Foua and Madaya. Syria's government vets U.N. aid plans on a monthly basis, and its late and partial approval of the programme for this month meant no aid had yet gone in, Stephen O'Brien said. "We are on Sept 9, and the supplies under the September plan have not yet started." As he spoke U.S. Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov were meeting nearbye for a third time in as many weeks to clinch a nationwide ceasefire deal. U.N. Syria envoy Staffan de Mistura, with de O'Brien, said the talks were "addressing complex, delicate and difficult issues. "The conclusions could make, lets's be frank, a major difference," he said. Helping around 250,000 people besieged in eastern Aleppo, where a battle for control has escalated in the past month, was becoming urgent, he said. "There is a growing concern about eastern Aleppo: the issue about food, the issue about the possibility that within perhaps the next few days it will turn out to be dark because there is no fuel, problems of water." Opposition groups say Russia, which co-sponsors the U.N. peace process, is part of the problem and not the solution, because it has provided strong air support for fighters loyal to Syrian President Bashar al-Assad. "We ask any party which has influence on any of the warring parties to ensure that they recognise that the demand for humanitarian access is paramount and rises above all the other vested interests," O'Brien said.