Russia and China have vetoed a European bid to target Syria at an angry UN Security Council meeting which exposed international divisions over Damascus's months-long crackdown on protests.
US ambassador Susan Rice led a rare walkout protest from the Security Council chamber when Syria's UN envoy accused the United States of being a party to "genocide".
After nearly six months of negotiations, nine countries voted for the text, drawn up by France, with Britain, Germany and Portugal. It called for "targeted measures" if Syrian President Bashar al-Assad did not end the assault on demonstrators, which the UN says has left at least 2,700 dead.
Russia and China used their veto as permanent members of the council to kill the resolution. South Africa, India, Brazil and Lebanon abstained, reaffirming a divide in the 15-nation body since NATO launched air strikes in Libya using UN resolutions to justify the action.
It is the first joint Russian-China veto since they blocked UN sanctions against Zimbabwe's President Robert Mugabe in July 2008.
In recent weeks, European negotiators had watered down a threat of immediate sanctions to possible "targeted measures" against Assad.
But Russia, which has a naval base in Syria, and China have both repeatedly threatened to veto any resolution which threatens sanctions.
Russia's UN envoy Vitaly Churkin said the European resolution was "based on a philosophy of confrontation." The threat of sanctions, which the resolution called "targeted measures," was "unacceptable," he added.
Chinese foreign ministry spokesman Ma Zhaoxu said the resolution aimed to "blindly impose pressure" on Syria, adding that neither the resolution nor the threat of sanctions would "help to ease the situation."
US ambassador Rice reacted with anger to Churkin's attack on the NATO campaign in Libya and accusations that it could be repeated in Syria.
"Let there be no doubt: this is not about military intervention. This is not about Libya," Rice told the council.
"That is a cheap ruse by those who would rather sell arms to the Syrian regime than stand with the Syrian people.
"The United States is outraged that this council has utterly failed to address an urgent moral challenge and a growing threat to regional peace and security," she said.
"Let me be clear. The United States believes it is past time that this council assumed its responsibilities and imposed tough targeted sanctions and an arms embargo on the Assad regime."
French ambassador Gerard Araud called the veto an "expression of disdain for the legitimate aspirations that are being fought for in Syria." Outside the chamber he called it a "vote against the Arab Spring."
But he vowed that the Europeans would not give up and that the veto would not give "carte blanche" to Assad.
While the United States and European Union have enacted their own sanctions, the Security Council has so far agreed only to non-binding statements on the crackdown.
Syrian Ambassador Bashar Jaafari slammed the move by Syria's "enemies."
He went on to condemn the Europeans for their role in the two World Wars and to accuse the United States of being a party to "genocide" by supporting Israel.
Rice and her delegation walked out in protest at Jaafari's prolonged attack. The British ambassador Mark Lyall Grant soon followed, leaving one of his deputies to listen.
Speaking to reporters after the vote, Lyall Grant said: "Those who blocked the resolution will have these actions on their conscience.
"These vetoes will be seen in the region as a decision to side with a brutal regime, rather than with the people of Syria, and it will be a bitter blow to all those Syrians who have implored the international community to take a stand."
Russia has drawn up its own resolution, condemning violence by the opposition as well as the government and calling for dialogue. The European nations said they would not even discuss it.