The United Nations Security Council is set to hold a special meeting Friday to assess whether aid workers have access to besieged areas in Syria as demanded last month by major world powers.

On May 17, members of the International Syria Support Group (ISSG) agreed in Vienna that starting June 1, the U.N. World Food Program (WFP) should air drop food, medicine and water to Syria's besieged communities if humanitarian access was denied by either side in the civil war.

The Syrian town of Daraya Tuesday was the first besieged town to receive a Red Cross convoy carrying some medical supplies, vaccines and nutritional items such as baby milk, Al Jazeera reported. The delivery, carried out by both U.N. and Syrian Arab Red Crescent staff, was the first since a government-imposed siege began in 2012.

Another convoy, containing only food supplies and no medicine, entered neighboring Moadamiyah. 

Last week U.N. humanitarian chief Stephen O'Brien told the 15-nation Security Council that the Syrian government and militant groups continued to block access to besieged areas, Reuters reported. Nearly 600,000 are reportedly trapped in these areas.

The United States, Britain and France are advocating air drops to areas inaccessible by land. Britain's Ambassador to the United Nations Matthew Rycroft reportedly said, “We need to press on with what the ISSG said about air drops. ... We have called for an emergency session of the council on Friday.”

The U.N. will formally talk about whether the obligation of access has been met. A decision will then be taken on the air drops. The meeting is scheduled to start at 10 a.m. EDT.

However, the U.N. and Russia have pointed to the less effective nature of air drops. The WFP carried out a 21-pallet air drop of aid to a government-held area of Deir al-Zour in eastern Syria February, which ended in failure. Of the 21, 10 were unaccounted for, seven landed in no man's land and four were damaged, reports said.

“It’s easier said than done,” Russian U.N. Ambassador Vitaly Churkin, said, according to Reuters.

Over 250,000 people have died in the Syrian civil war. Millions have fled their homes and many are living as refugees.