Wrangling between the United States and Russia over the Syria crisis left the UN Security Council even further from reaching an accord on ways to end the bloodshed, diplomats said.
Council members are now waiting to see if President Bashar al-Assad keeps a commitment to respond by Tuesday to proposals made by UN-Arab League envoy Kofi Annan to end the killing, diplomats said.
The United States, Britain, France and Germany led calls for Russia and China to agree a Security Council resolution condemning the violence, which the UN says has left well over 7,500 dead in the past year.
But Russia's Foreign Minister Sergei Lavrov said the West's "ultimatums will not work" as he rebuffed pressure at a special council meeting on the Arab Spring uprisings.
"I add my voice to that of Mr Annan in urging President Assad to act swiftly, within the next few days, in response to the proposals put forward" by the envoy, UN Secretary General Ban Ki-moon told the meeting.
"I appeal to the Security Council to unite strongly behind ending the violence and supporting Mr. Annan's mission to help Syria pull back from the brink of a deeper catastrophe," he added.
Assad has until Tuesday to give a response to peace proposals made by Annan, diplomats said.
Annan said on leaving Damascus on Sunday that he had made "concrete proposals" to Assad on ending the killing in Syria and securing humanitarian access to protest cities.
French Foreign Minister Alain Juppe said the Syrian president had agreed to give an answer within "48 hours". Senior diplomatic sources confirmed that a response was expected by early Tuesday.
Russia and China have twice used their powers as permanent Security Council members to veto resolutions on Syria, saying they were unbalanced and only sought regime change.
The Western powers are now waiting to see if Assad replies to decide whether to step up negotiations with Russia and China on a new attempt to pass a resolution, diplomats said.
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The United States, Britain and France heightened their condemnation of Assad at Monday's special ministerial meeting and urged Russia and China to agree a resolution.
"How cynical that, even as Assad was receiving former secretary general Kofi Annan, the Syrian army was conducting a fresh assault on Idlib and continuing its aggression in Hama, Homs, and Rastan," US Secretary of State Hillary Clinton told the meeting.
Clinton said after the meeting that she believed her Russian counterpart Lavrov, had heard "how strong the feelings are" and "that we expect all nations including Russia and China to join us now in pressing the Assad regime to silence the guns."
France's Juppe appealed directly to Russia and China, while also calling on the council to order an International Criminal Court investigation into the Syria crackdown.
"I appeal to China and Russia to hear the voices of the Arabs and the world conscience and join us," Juppe said.
"The situation in Syria casts a long shadow over this debate," declared Britain's Foreign Secretary William Hague, whose country organized the debate as president of the Security Council for March.
But Lavrov said change in the Arab world "must not be achieved by misleading the international community or manipulating the Security Council."
He condemned "hasty demands for regime change" and "unilateral sanctions" as "risky recipes of geopolitical engineering which can only result in a spread of the conflict."
China's UN envoy Li Baodong insisted there could be no military intervention in Syria and denied that "self-interests" had motivated his country's veto of the two resolutions.
"No external parties should engage in military intervention in Syria and push for regime change," Li told the meeting.
Juppe told reporters that if Assad reacted to the UN proposals, the Security Council members would resume talks on a resolution condemning the Syrian government.
Diplomats said that, with the Syrian conflict already one year old, the Security Council could still take weeks to pass its first resolution on the crisis.