Updated at 3:07 p.m. ET
(CBS/AP) UNITED NATIONS - Russia and China again vetoed a Western-backed U.N. resolution Thursday aimed at pressuring President Bashar Assad's government to end the escalating 16-month conflict in Syria.
The 11-2 vote, with two abstentions from South Africa and Pakistan, was the third double veto of a resolution addressing the Syria crisis by Damascus' most important allies.
The defeat leaves in limbo the future of the 300-strong U.N. observer mission in Syria, which was forced to suspend operations because of the intensified fighting. Its mandate, to monitor a cease-fire and implementation of international envoy Kofi Annan's peace plan, expires Friday.
"The stakes are high," said CBS News foreign affairs analyst Pamela Falk, "because the stalemate at the U.N. means that an international plan for a peaceful transition is not available."
A frustrated White House declared that Russia and China placed themselves on the "wrong side of history" and the "wrong side of the Syrian people." White House spokesman Jay Carney told reporters aboard Air Force One that the vote was "regrettable" and "highly unfortunate."
Carney said the lack of U.N consensus "will have repercussions for the countries that vetoed the resolution for a long time in terms of how they're viewed by the Syrian people. Because there is no doubt that Syria's future will not include Bashar Assad."
He added: "It is a mistake to prop up that regime as it comes to an end."
Britain's U.N. Ambassador Mark Lyall Grant, who sponsored the Western-backed draft, said he was "appalled" at the third double veto of a resolution aimed at bringing an end to the bloodshed in Syria and creating conditions for political talks. The resolution had threatened sanctions if the Syrian regime didn't quickly stop using heavy weapons.
"The consequence of their decision is obvious," he said. "Further bloodshed, and the likelihood of descent into all-out civil war." Activists say more than 17,000 people have been killed since the uprising began in March 2011, most of them civilians.
"The consequence of today's action is the situation will continue to deteriorate," U.S. Ambassador Susan Rice told reporters.
Russia's U.N. Ambassador Vitaly Churkin said the resolution should never have been put to a vote because the sponsors knew it had no chance of adoption.
"We simply cannot accept a document under Chapter 7, one which would open the path for the pressure of sanctions and further to external military involvement in Syrian domestic affairs," he said.
The latest veto was a blow to 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 has been flouted by the Assad government.
The vote on the resolution was originally scheduled for Wednesday, but Annan requested a delay and appealed to the council to unite behind a new resolution. 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.
Wednesday's delay was announced shortly after the deadly bombing of a high-level security meeting in Damascus that has made Assad's hold on power look increasingly tenuous.
Speculation is rampant as to Assad's whereabouts, CBS News correspondent Clarissa Wardon "CBS This Morning" Thursday, though Syrian state TV said Assad attended the swearing-in of his new defense minister.
Some opposition members said left Damascus for the heartland of his Alawite tribe in the coastal city of Latakia, Ward reports. That claim seems unlikely, however, given that Assad's security apparatus is in Damascus and a move to Latakia would appear as the president conceding his capital and backing away from the fight.
One thing is certain, Assad finds himself in an uncomfortable position, Ward reports. He no longer knows who he can trust, and the rebel Free Syrian Army is touting the deadly bomb attack as a major triumph, even calling it the beginning of the end for the Assad regime.
At the U.N., a frustrated, angry Lyall Grant said the attacks in Damascus over the last 48 hours "demonstrate the need for urgent and decisive action by the Security Council to stop the downward spiral into chaos which will claim many more innocent lives and affect the stability of the region."
Annan's spokesman Ahmad Fawzi said the envoy "is disappointed that at this critical stage the U.N. Security Council could not unite and take the strong and concerted action he had urged and hoped for."
Churkin told the council he would not put Moscow's rival draft resolution to a vote to avoid continuing confrontation in the Security Council. Moscow's proposal called for the "immediate implementation" of Annan's plan and guidelines for a political transition approved at a meeting in Geneva last month and would have extended the observer mission for 90 days, but it made no mention of sanctions.
Instead, Churkin proposed that council members adopt "a brief depoliticized resolution" extending the mission of the unarmed observers for a limited time to preserve its "useful potential."