Russia on Thursday accused US diplomats of blocking a UN Security Council condemnation of a bomb attack in the Syrian capital that left at least 59 dead.
Russia's UN mission said the United States "encourages" militant attacks by blocking the council's statements on attacks in Syria. Diplomats said however that Russia had in turn refused to include language criticizing ally President Bashar al-Assad.
The bomb near the offices of Assad's ruling party in Damascus also badly damaged the Russian embassy. Syrian activists said at least 59 people were killed.
The 15-member council held talks on a statement proposed by Russia but the United States and other western nations had wanted to include criticism of Assad's forces for attacking civilians, UN diplomats said. Russia refused this, they added.
"The text confirmed the unshakable principles that terrorism in all its forms and manifestations constitutes one of the most serious threats to international peace and security and has no justification," said Anton Uspensky, spokesman for Russia's UN mission.
"Unfortunately, such an indispensable reaction by the Security Council to this terrorist attack has been once again blocked by the US delegation linking it with other questions," he added.
"We consider unacceptable this search for justifications for terrorist actions. It is obvious that by doing so the US delegation encourages those who have been repeatedly targeting American interests, including US diplomatic missions," he said.
US mission spokeswoman Erin Peltin said: "We strongly condemn all indiscriminate terrorist attacks against civilians or against diplomatic facilities.
"We agreed with the Russian draft of a statement from the Security Council and only sought to add similar language on the regime's brutal attacks against the Syrian people. Unfortunately, Russia refused to engage on a credible text," she added.
The council normally condemns attacks on diplomatic missions. But it has been badly divided by the 23-month Syrian conflict which has left more than 70,000 dead, according to the UN.
Russia and China have blocked three council resolutions which would have increased pressure on Assad to end hostilities.
UN leader Ban Ki-moon condemned the attack and others in the Syrian capital.
"The secretary general reiterates his firm conviction that resorting to violence and military means will only lead to more suffering and destruction, and that a political solution is the only way out," said his spokesman Martin Nesirky.
Meanwhile, the United Nations confirmed that UN-Arab League mediator Lakhdar Brahimi will pursue efforts to broker an end to the war at least until the end of 2013.
Brahimi's first six-month mission ends on Friday, but Nesirky said the contracts of Brahimi and his team had been extended until the end of the year.