Syria has given approval for humanitarian convoys to reach all of the country's 19 besieged areas by the end of this month, the UN said Thursday, but warned "approval...does not mean delivery."

"We were informed by our team in Damascus that basically there has been a permission, an approval... by the government of Syria for all 19 besieged areas," the United Nations envoy to the war-racked country, Staffan de Mistura, told reporters. 

He stressed that Syria has given such approvals in the past before ultimately blocking convoys from distributing life-saving supplies.