The United Nations should be able to deliver aid to all of Syria's 18 besieged areas within a week, a senior UN official said Thursday, February 18, after life-saving supplies reached five locations, AFP reports.

Jan Egeland, who is the special advisor to the UN's Syria envoy Staffan de Mistura, made the comments after a meeting of representatives from the 17-nation International Syria Support Group (ISSG).

"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 said that there was plan to deliver aid to the eastern city Deir ez-Zor, the majority of which is controlled by the Islamic State group (IS) and where an estimated 200,000 people still live.

The UN official said the World Food Programme "has now a concrete plan" to conduct humanitarian air drops over the city and that this prospective operation has the support of both the United States and Russia.

Russian cargo planes reportedly delivered humanitarian aid to regime-held neighbourhoods in Deir ez-Zor last week.