Russia faces mounting pressure to intervene in the spiralling Syria crisis today, as a top British diplomat urged Moscow to "get off the fence" or see a bloody civil war erupt and spread to other nations.
Mark Lyall Grant, UK ambassador to the United Nations, warned that unless Russia wields its influence "we are coming to the end of the shelf life of the peace plan with all the horrible alternatives that that means".
Violence continued yesterday with reports of another mass execution emerging as the UN Human Rights Council demanded an investigation into the massacre in Houla of more than 100 civilians, including children, apparently by pro-regime militias.
British Foreign Secretary William Hague accused the Assad regime of possible crimes against humanity and refused to rule out the use of military force - though he said Kofi Annan's six-point peace plan remained the best possible solution.
Russia however backs the regime's conclusion that the massacre was the work of "extremists" and along with China was one of the few countries not to approve the UN resolution condemning the killings.
President Vladimir Putin denied supporting the regime or supplying weapons and struck what observers saw as a more conciliatory tone, but continued to resist stronger UN action.
Grant said that without that Russian support, Syria would descend into a bloody civil war that would almost inevitably spread to Lebanon and beyond and become a "proxy" war involving Iran.
The coming weeks - including meetings such as the forthcoming G20 summit - would show "whether Russia is really willing to work with us", he told Australia's ABC National Radio.
"Otherwise I do fear that we are coming to the end of the shelf life of the peace plan with all the horrible alternatives that that means.
"There is certainly a risk that if the Annan plan definitively fails then we will head for a very bloody civil war and that civil war will inevitably become something of a proxy war, with some sides supporting the regime and some sides supporting the opposition, and it will almost certainly spill over into Lebanon and perhaps into some other neighbouring countries as well.
It was vital to "ramp up the political pressure" on president Assad to come to the table, he said.
"There is no sign of that happening at the moment, but one of the reasons there is no sign is that Russia has not yet unequivocally come off the fence and said that it is going to exert its own diplomatic and bilateral pressure, or influence - which is very considerable - on Damascus behind that.
"If Russia did make that effort then that would make a significant difference."
Earlier, Mr Hague met with Syrian opposition groups and urged them to build a united coalition against the "murderous" Assad regime, warning the country stood "on the brink" of all-out civil war.
Speaking from Istanbul, where he also met UN secretary general Ban Ki-moon, he said, there was a "desperate need for a political solution in Syria."
Asked if the international community could intervene militarily, he said: "We are not ruling anything out.
"But a military intervention in Syria, as I have always pointed out, would have to be on a vastly greater scale than was the case in Libya and it would have to enjoy broad international support.
"So we are not at that stage at this point now."