A crowd waits on the edge of a buffer zone that was created in preparation for a food aid distribution in the besieged town of Moadamiyeh, Syria, which was a joint operation between the Syrian Arab Red Crescent (SARC) and the International Committee of the Red Cross (ICRC) Wednesday, February 3, 2016. REUTERS/Pawel Krzysiek/ICRC/Handout via Reuters

The United Nations aims to deliver aid to all of Syria’s 18 besieged areas within a week, making its first air drops of food aid in Syria, to Deir al-Zor, an eastern town of 200,000 besieged by ISIS militants, the chair of a U.N. humanitarian task force said on Thursday.

U.N. aid agencies do not have direct access to areas held by ISIS, including Deir al-Zor, where civilians face severe food shortages and sharply deteriorating conditions. Yet, U.N. aid convoys reached five areas already as Russian cargo planes had reportedly delivered humanitarian aid to regime-held neighborhoods in Deir Ezzor last week in a mission that included 114 trucks and delivered supplies to an estimated 80,000 people.

Jan Egeland, the special advisor to the UN’s Syria envoy Staffan de Mistura, after a meeting of representatives from the 17-nation International Syria Support Group (ISSG), told reporters that the U.N.’s World Food Programme (WFP) had a “concrete plan” for carrying out the Deir al-Zor operation in coming days.

He said the WFP hoped to make progress reaching “the poor people inside Deir al-Zor, which is besieged by Islamic State. That can only be done by air drops,” said Egeland.

“We discussed the next phase which is to reach all of the remaining besieged areas of Syria. And we should be able to do (so) before the next meeting which will be in a week,” Egeland said.

Egeland gave no details of the costly air operation but said that “It’s a complicated operation and would be in many ways the first of its kind”.

Egeland, who is also head of the Norwegian Refugee Council, later told Reuters in Oslo: “It is either airdrops or nothing. Airdrops are a desperate measure in desperate times.”

A WFP official was not available to comment on where cargo planes would depart from or what they would carry.

There are more than 480,000 Syrians living in areas besieged by the government, militant groups and terrorist forces, according to the UN. Over four million others are living in what the UN defines as “hard-to-reach” areas.

“The people of Syria … have waited too long for relief,” Egeland told reporters following the meeting in Geneva.