The United Nations Security Council's five permanent members ended a tense meeting fiercely divided over a British-proposed resolution sanctioning the use of military force to punish Syria for its alleged use of chemical weapons.
Russia and China remained firmly opposed as the meeting ended with no indication of whether the resolution would ever be put to a Security Council vote.
US officials in Washington and the United Nations indicated the resolution appeared doomed and any action against Syria would have to occur without the backing of the council.
US ambassador Samantha Power criticised the Russians and Chinese in a series of Twitter messages, saying their refusal to back the British draft was their latest effort to block action against the regime of Syrian president Bashar Assad.
"Unfortunate outcome of P5 meeting: Russia & China continue to block meaningful Security Council action on #Syria, impeding UN path forward," she wrote.
Earlier, Ms Power left the meeting of the permanent five council members without commenting, as did envoys of Britain, France, Russia and China.
The draft resolution was sent back to the governments of the five countries for consultations, according to a Western diplomat.
The United States, Britain and France have blamed the Assad regime for the alleged deadly chemical weapons attack near Damascus last week.
The US has not presented concrete proof, and UN inspectors currently in Syria to investigate alleged chemical attacks have not endorsed the allegations. But President Barack Obama said last night that the US had concluded that the Syrian government was responsible.
The Russian government has condemned the idea of striking against Syria before the inspectors present their findings and have warned that acting without Security Council authorisation would be illegal.
The US and its allies have questioned the ability of the UN team to conduct a meaningful investigation, saying they have faced too many delays in Syria.
US State Department spokeswoman Marie Harf said Washington expected no progress at the United Nations.
"We heard nothing different from the Russians in today's meeting than we have for months and indeed years about Syria," she said. "So we have no reason to believe that efforts at the Security Council would be any different than these previous efforts that have failed."
A spokesman for Prime Minister David Cameron said in London that the British draft resolution would authorise "all necessary measures under Chapter 7 of the UN Charter to protect civilians from chemical weapons". Chapter 7 allows the use of international armed force to back up UN decisions.
An anonymous US official said the Obama administration tried to discourage the British government from pushing the resolution. The official said Washington believed the effort would be futile because of Russia's opposition and introducing it could lend credibility to the argument that UN authorisation is required for action against Syria.
Speaking from The Hague yesterday, UN secretary general Ban Ki-moon said no action should be taken until the UN chemical weapons inspectors finished their work.
"Let them conclude ... their work for four days and then we will have to analyse scientifically" their findings and send a report to the Security Council, he said.
The UN said the analysis would be done "as quickly as possible".
Mr Ban also pleaded for more time to give diplomacy another chance to end the more than two-year conflict that has killed more than 100,000 people. But he added that the Security Council must not go "missing in action".
Syria's ambassador to the UN Bashar Ja'afari, meanwhile, said he sent a letter to Mr Ban demanding that the UN experts extend their investigation to what he described as three chemical weapons attacks against Syrian soldiers in Damascus suburbs.
He said the attacks occurred on August 22, 24, and 25 and that dozens of Syrian soldiers were currently being treated for inhaling nerve gases.
He also expressed confidence that the British draft resolution would no nowhere because members of the councils "don't believe the authenticity of the allegations" against Syria, a reference to Russia and China.
Mr Ja'afari reiterated his denial that the Syrian government was behind any of the attacks. "The Syrian government is innocent of these allegations," he said.