UNITED NATIONS – The U.N. Security Council failed again Saturday to take decisive action to stop the escalating violence in Syria as Russia and China vetoed a resolution backing an Arab League plan that calls for President Bashar Assad to step down.

The other 13 members of the council, including the United States, Britain and France, voted in an unusual weekend session in favor of the resolution aimed at stopping the ongoing violence in Syria.

It was the second time in four months that Russia and China used their veto power to block a Security Council resolution condemning the violence in Syria.

The rare double-veto was issued following days of talks aimed at overcoming Russian opposition to the draft resolution. Several European envoys said before the session that despite Russia’s attempts to seek a delay, they felt compelled to call for the vote because they were concerned about the escalating violence by Assad’s regime.

The urgency was heightened by an assault by Syrian forces firing mortars and artillery on the city of Homs. Activists said more than 200 people were killed in what they called one of the bloodiest episodes of the uprising against Assad. The U.N. says more than 5,400 people have been killed over almost 11 months in a government crackdown on civilian protests.

After the vote, U.S. Ambassador Susan Rice, in unusually strong language, said the United States was “disgusted” by the outcome of the vote.

“For months this council has been held hostage by a couple of members,” Rice said. “These members stand behind empty arguments and individual interests while delaying and seeking to strip bare any text that would pressure Assad to change his actions.

“This intransigence is even more shameful when you consider that at least one of these members continues to deliver weapons to Assad,” she added, referring to Russia, a major arms supplier for Syria.

Both President Obama and Secretary of State Hillary Clinton had urged passage of the resolution earlier Saturday.

Syria has been a key Russian ally since Soviet times, and Moscow has opposed any U.N. call that could be interpreted as advocating military intervention or regime change.

Moroccan Ambassador Mohammed Loulichki, a key sponsor of the resolution, told reporters afterward that his country was “frustrated and sad” over the outcome. He said the draft remains on the table, and he hopes that consensus can still be reached to take another vote later.

The latest U.N. resolution repeated all the conditions that Arab League foreign ministers set in a Jan. 22 decision on Syria, calling for a Syrian-led political transition in which Assad would delegate his powers to a deputy.

Russia had expressed concerns about the draft text, saying it feared the resolution would lead to the kind of military intervention and regime change seen in Libya after last year’s council action intended to protect civilians from attacks by forces loyal to strongman Moammar Gadhafi.

After Saturday’s vote, Russian Ambassador Vitaly Churkin accused fellow council members of being inflexible.

Churkin said his country’s proposed amendments to the resolution had been ignored, and the version voted on Saturday “did not adequately reflect the real state of affairs in Syria.”