Geneva: The US and Russia have not been cooperating to solve Syrian humanitarian problems recently, despite a ceasefire and 13 illegal sieges amounting to “strangulation of the civilian population”, a senior UN official said on Thursday.

Jan Egeland, the UN humanitarian adviser on Syria, said US-Russian co-leadership had been “great” last year, but he had not seen it of late.

He hoped they would join Turkey and Iran in pushing for breaking the “horrific gridlock” of aid convoys in upcoming Syria peace talks in Astana and Geneva.