A handout picture released by the Syrian opposition's Shaam News...

A handout picture released by the Syrian opposition's Shaam News Network allegedly shows forces loyal to Syria's President Bashar al-Assad being transported in a military vehicle in central Damascus. (July 16, 2012) Credit: AFP/Getty Images

 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 11-2 vote, with two abstentions from South Africa and Pakistan, was the third double veto of a Syria resolution by Damascus' most important allies.

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.

It was a blow to Kofi Annan, the joint U.N.-Arab League envoy to Syria, who had called for "consequences" for non-compliance with his six-point peace plan, which the Assad government has flouted.

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.

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