The UN Security Council braced for a showdown over Syria on Tuesday, with US Secretary of State Hillary Clinton leading a Western charge pressing Russia to back action to stop the violence.
The meeting is taking place amid a surge of violence in Syria on Monday, mostly in the flashpoint Homs region, killed almost 100 people, including 55 civilians, the Syrian Observatory for Human Rights said.
The violence, which also saw 25 soldiers killed, marks one of the bloodiest days of the revolt against President Bashar al-Assad's regime since it erupted in March.
Amid opposition warnings of a potential massacre, Clinton, the head of the Arab League and the British and French foreign ministers headed to New York to push forward a UN resolution.
But Russia, which has veto-power in the council, has objected to a resolution introduced by Morocco under which Syrian President Bashar al-Assad would accept a ceasefire and hand over power to a deputy ahead of talks.
"The United States condemns in the strongest possible terms the escalation of the Syrian regime's violent and brutal attacks on its own people," Clinton said in a statement Monday announcing her trip to the United Nations.
"The Security Council must act and make clear to the Syrian regime that the world community views its actions as a threat to peace and security. The violence must end, so that a new period of democratic transition can begin."
European Union leaders at a Brussels summit unanimously voiced outrage over the bloodshed in Syria. EU President Herman Van Rompuy called on the Security Council to "take long overdue steps to bring an end to the repression."
British Prime Minister David Cameron, citing reports that more than 400 children have been killed in the crackdown, said: "It's frankly an appalling situation."
"It's time for all the members of the UN Security Council to live up to their responsibilities instead of shielding those with blood on their hands," Cameron said.
Syria's foreign ministry fired back, saying "the aggressive American and Western statements against Syria are escalating in a scandalous manner," and again blaming the recent violence on "armed terrorist groups."
Russia and China -- which have accused Western nations of misusing a UN mandate in their intervention to bring down Libyan strongman Moamer Kadhafi -- in October vetoed an earlier Western-backed draft resolution on Syria.
Russian Deputy Foreign Minister Gennady Gatilov expressed similar concerns about the latest draft resolution. Russia has longstanding ties to Syria and is the main supplier of weapons to Assad's regime.
"The draft has statements in it calling on the member states to stop arms deliveries to Syria," Gatilov told Interfax news agency in an interview.
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"But there is no clear line between arms contraband that some countries engage in to support extremist forces in Syria, and the legal military-technical ties with this country," he said.
Russia has instead called for Assad's regime and the opposition to hold "informal contacts" in Moscow without any preconditions.
Asked about Russia's call for talks, White House spokesman Jay Carney said the United States supported a political solution but was "intensely discussing" with Russia the "real deterioration on the ground" in Syria.
"The regime has lost control of the country and will eventually fall," Carney said.
Human rights groups say that more than 5,400 people have died in Syria as Assad has tried to crush the latest in a wave of Arab uprisings that last year overthrew authoritarian leaders in Egypt, Libya and Tunisia.
Activists said that another 53 people were killed on Monday -- 35 of them civilians -- a day after 80 people were reported to have fallen in some of the most intense clashes since anti-Assad protests erupted 10 months ago.
Regime forces appeared determined to wrest back control of Damascus suburbs which have intermittently fallen into the hands of the rebels and were reported to have executed a founder of the rebel army.
Troops penetrated Rankus, 40 kilometers (25 miles) north of the capital, after having shelled the town, which the army had encircled for the past six days, rights groups said.
The opposition Syrian National Council warned of the potential for a massacre in Rankus after hundreds of young men were rounded up by security forces.
"They have imposed a siege on Rankus, preventing food and medical aid from entering" the town of 25,000 inhabitants, it said in a statement.
Before heading to New York, Arab League chief Nabil al-Arabi urged Russia and China to change their position, saying that deteriorating conditions had led Arab monitors to suspend their mission to Syria.
In Paris, French foreign ministry spokesman Bernard Valero urged action against "the Syrian regime's savage repression."
A French diplomat, speaking on condition of anonymity, said that opinions have "evolved" within the council and at least 10 of the 15 members could vote in favor of the draft resolution.
Russia and India were the most hostile to the resolution, the diplomat said.