BEIRUT - Syria is nearing full-blown sectarian civil war that would be catastrophic for the entire Middle East, Western nations said on Thursday, urging Russia to end its support for President Bashar al-Assad and put pressure on him to stop the bloodshed.
With anti-Assad rebels urging international envoy Kofi Annan to declare his peace plan dead, freeing them from any commitment to the tattered truce, U.S. Secretary of State Hillary Clinton said the prospect of spiralling violence presented "terrible" danger.
"A civil war in a country that would be riven by sectarian divides ... could then morph into a proxy war in the region because, remember, you have Iran deeply embedded in Syria," Clinton said during a trip to Copenhagen where she urged Moscow to increase pressure on Assad.
Russia, like China, has vetoed two Security Council resolutions calling for tougher action against Damascus, while stressing hopes that Annan's plan can spur a political solution. Washington called a reported shipment of Russian arms to Syria "reprehensible" although not illegal.
"The Russians keep telling us they want to do everything they can to avoid a civil war because they believe that the violence would be catastrophic," Clinton said.
"I think they are in effect propping up the regime at a time when we should be working on a political transition."
British Foreign Secretary William Hague said Syria was moving towards "all-out civil war or a state of collapse". The European Union was drafting new sanctions against Syria, he added, calling on other nations to pressure Assad.
A bloody crackdown on what began 14 months ago as a peaceful mass uprising has increasingly turned it into an armed conflict between heavily armed forces representing an establishment dominated by Assad's Alawite minority, an offshoot of Shi'ite Islam, and rebel forces drawn largely from the Sunni majority.
Damascus says the rebels are backed by Sunni-ruled Gulf Arab states fearful of the growing influence of Syria's main ally in the region, Shi'ite Iran.
U.N. Secretary-General Ban Ki-moon warned that another massacre like Friday's killing of 108 men, women and children in the western Houla region could pitch Syria into a devastating civil war "from which the country would never recover".
The United Nations has said the army and pro-Assad gunmen were probably responsible for the Houla killings, but Syria said on Thursday that a preliminary investigation had shown that anti-government armed groups carried out the killings with the aim of encouraging foreign military intervention.
Washington's U.N. ambassador, Susan Rice, said Syria's version of what had happened in Houla was "another blatant lie". The massacre led a range of Western countries to expel senior Syrian diplomats and to press Russia and China to allow tougher action by the U.N. Security Council.
Syria's main rebel commander, Colonel Riad al-Asaad, urged Annan to declare that his peace plan had failed.