Russia blocked a U.N. Security Council statement on Thursday that would have condemned the government of Syrian President Bashar al-Assad for recent missile and "barrel bomb" attacks on civilians, including children, U.N. diplomats said, Reuters reported.
The council's failure to approve the U.S.-drafted statement elicited an angry reaction from Washington.
"We are very disappointed that a Security Council statement expressing our collective outrage at the brutal and indiscriminate tactics employed by the Syrian regime against civilians has been blocked," said Kurtis Cooper, a spokesman for the U.S. mission to the United Nations.
"These barrel bombs - and the explosive materials contained within them - further underscore the brutality of the Assad regime and the lengths they will go to attack and kill their own people, including women and children," he said.
"Surely, at a minimum, the Security Council should be able to condemn such barbarities," Cooper added.
He did not say who blocked the statement, though several council diplomats said on condition of anonymity that the Russian delegation demanded the removal of any reference to the Assad government in the draft statement, after which Western council members decided to withdraw the proposed text.
A spokesman for the Russian mission declined to comment.
The draft statement would have expressed "deep concern at the escalating level of violence in the Syrian conflict and condemned all violence by all parties" and "outrage" at Syrian government airstrikes that the text said killed over 100 people, including many children.
The statement would have also welcomed the convening of a peace conference in Switzerland on January 22, which delegations representing the Syrian government and the rebels are expected to attend.
Russia, a staunch ally of Assad, has joined with China in vetoing three Security Council resolutions that would have condemned Assad's government and threatened it with sanctions.
The longstanding deadlock on the Security Council was briefly broken in late September and early October when the 15-nation body agreed a resolution demanding the eradication of Syria's chemical weapons program and a statement calling for increased aid access and humanitarian pauses in the fighting.
One of the main reasons for the sudden agreement earlier this year, diplomats say, was U.S. President Barack Obama's threats to launch missile strikes against Syria for an August 21 sarin gas attack that killed hundreds. Washington and its European allies blamed Assad's forces for the August 21 incident, while the government said the rebels were responsible.
More than 100,000 people have been killed and millions forced from their homes in Syria's civil war, which is now in its third year.