Russia and China again vetoed a Western-backed U.N. resolution Thursday threatening sanctions against President Bashar Assad's government if it didn't stop using heavy weapons in the escalating 16-month conflict.
The vote also leaves in limbo the future of the 300-strong U.N. observer mission in Syria, whose mandate expires Friday.
Britain's U.N. Ambassador Mark Lyall Grant, who sponsored the Western-backed draft, said he was "appalled" at the third double veto by Russia and China.
Annan had requested a delay in Wednesday's vote on the resolution and appealed to the council to unite behind a new resolution, but Moscow wouldn't budge and the West insisted on including the threat of non-military sanctions under Chapter 7 of the U.N. Charter.
That could eventually open the door to the use of military force.