The Office of the Coordination of Humanitarian Affairs said in a release it has made several requests to the government of President Bashar Assad for access to those in need of aid. Aid convoys have been rescheduled seven times since March, the agency said.
Officials estimate 1.2 million people in the Damascus region need assistance.
The office also appealed this week for $4.4 billion in aid for Syria, the largest appeal in its history. Lebanon is seeking an additional $450 million and Jordan $350 million to help support refugees now living within their borders.