Russia and China have vetoed a UN Security Council resolution that threatened Syrian authorities with sanctions over use of deadly force against civilians in the ongoing conflict.
The vote was held on Thursday, with 11 countries voting in favour, two against, and two more abstaining. It is the third resolution to be vetoed by the two countries, both Syria's key allies, in nine months.
The Security Council comprises 15 members, five of which are permanent members with powers to veto resolutions.
"The United Kingdom is appalled at the veto of Russia and China," said Britain's UN envoy Mark Lyall Grant, whose country took the lead in writing up the resolution.
The United States condemned the move as a "highly regrettable decision".
It is a "mistake to prop up that regime", said Jay Carney, President Barack Obama's spokesman, at a White House briefing shortly after the resolution was vetoed.
The vetoed resolution would have extended a UN observer mission in Syria for 45 days. The mission has been largely ineffectual as its work had to depend on a ceasefire brokered by UN-Arab League envoy Kofi Annan, but which never materialised.
The Security Council still has time to negotiate another resolution on the fate of the unarmed mission before its initial
90-day mandate expires at midnight (0400 GMT) on Friday.
Although the resolution sought to impose non-military sanctions, it incorporated Chapter VII of the UN charter which allows the council to authorise actions ranging from diplomatic and economic sanctions to military intervention.
Western council members have said they are talking about a threat of sanctions on Syria, not military intervention.
Al Jazeera's Alan Fisher, reporting from the UN headquarters in New York, said it was an acrimonious meeting.
"This is a very angry meeting of the UN Security Council. The German ambassador was incredibly critical of the Russian position, but he was reserved when you put it against the comments made by the French ambassador," he said.
"What we're seeing is a cycle of talks, votes, vetoes of condemnation and no one seems to be coming with a plan ... that can break this cycle at the moment."
The text was backed by the United States, France, Germany and Portugal.
In-depth coverage of escalating violence across Syria
Russia had said it could not accept sanctions, and accused Western nations of being behind a resolution that sought to "open the path to the pressure of sanctions and further ... external military involvement in Syrian domestic affairs".
"Their calculations to use the UN Security Council to further their plans to put their pressure on sovereign states will not pass," Vitaly Churkin, Russia's ambassador to the UN, said on Thursday.
In the run-up to the vote, Annan travelled to Russia and met with Vladimir Putin, the president, and Sergei Lavrov, his foreign minister, to try to get Moscow to back tougher action against Syria.
Annan was "disappointed" at the council's failure to press for an end of the Syria conflict, his spokesman said.
The conflict, which began 16 months ago as an uprising against Bashar al-Assad's regime, has killed at least 14,000 people, according to UN estimates. Many have been killed by security forces.