The United States is calling on UN Security Council members to vote for increased access to quake-stricken Syria by opening more border crossings from Turkey.

Under a current Security Council mandate, aid workers can only use one route to enter rebel-held northwest Syria from Turkey. United Nations officials say the political issue is jeopardizing aid efforts.

UN Special Envoy for Syria Geir Pedersen stressed, "We are mobilizing funding and we are trying to tell everyone, put politics aside. This is the time to unite behind a common effort to support the Syrian people."

Washington wants an immediate vote on authorizing more border crossings, saying it's ready to provide any and all aid to the people of Syria.

UN aid chief Martin Griffiths tweeted that people in north-west Syria "feel abandoned." He says he wants to correct "this failure" as quickly as possible.