"The idea was to deliver aid before Vienna [meeting of ISSG], but it has not happened. It has to happen today or tomorrow early morning. If not, there will be only negative reports [from the UN side on the humanitarian access issue] to the ISSG in Vienna," Egeland said.
"In case of Daraya, it [pressure] should be on Damascus, as they are the ones who have blocked it. But we also have problems with an assessment mission to Foah and Kefraya. They also did not have access, and that was because of the opposition groups," he said.
Syria has been mired in civil war since 2011, with government forces loyal to Syrian President Bashar Assad fighting numerous opposition factions and extremist groups.
A US-Russia-brokered ceasefire came into force across Syria on February 27, but it does not apply to terrorist organizations active in the country, such as Nusra Front, which is outlawed in many countries, including Russia. Despite the ceasefire agreement, violence has escalated in Syria in recent weeks, especially in the northern Aleppo region.