Russia has vetoed a Western-backed emergency UN Security Council resolution condemning the Crimea referendum but China has abstained, isolating Moscow further on the Ukraine crisis.
The draft resolution, which says Sunday's referendum would have no validity, got 13 votes in the 15-member council. But it was rejected when permanent member Russia exercised its veto.
"Russia isolated, alone and wrong blocked the resolution's passage," US ambassador Samantha Power told the Council at its seventh emergency session on Ukraine since the crisis began.
"This is a sad and remarkable moment," she said.
"As we speak, Russian armed forces are massing across Ukraine's eastern border," she added in a short speech.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
China often backs Russia at the council, especially on Syria-related votes, and Western diplomats had seen its abstention as the best possible outcome from the vote.
When the Security Council ruled on a similar international crisis, between Russia and Georgia in 2008, Beijing abstained.
Saturday's emergency meeting was called at Washington's request and the resolution had been drafted by the United States in very measured terms so that it could be accepted by Beijing.
The resolution declared that the referendum on Crimea coming under Kremlin rule has "no validity and cannot form the basis for any alteration of the status of Crimea".
