UNITED NATIONS — The United Nations plans to make 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.

Jan Egeland, speaking to reporters in Geneva a day after U.N. aid convoys reached five areas, some besieged by government forces and others by rebels, said the U.N.’s World Food Programme (WFP) had a “concrete plan” for carrying out the Deir al-Zor drop in the coming days.

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

“It’s a complicated operation and would be in many ways the first of its kind,” Egeland said, giving no details of the air operation, which is far more costly than land convoys.

Egeland, who is 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.”

U.N. Syria envoy Staffan de Mistura suggested air drops could also relieve civilians in other besieged areas.