Associated Press

WASHINGTON (AP) - The Obama administration has closed the U.S. Embassy in Damascus and pulled all American diplomats out of Syria.

Officials say Ambassador Robert Ford and other diplomats left Syria on Monday. It's the most dramatic U.S. move so far after 11 months of a violent crackdown on dissent by President Bashar Assad's regime.

The State Department warned last month it would close the embassy unless Assad's government stepped up its protection. It cited concerns about the safety of personnel and recent car bombs.

The U.N. says Assad's crackdown has killed more than 5,400 people since March. The revolt began with mostly peaceful protests, but armed rebels are now increasingly fighting the regime.

The Obama administration has long demanded that Assad step down. Officials insist his regime's demise is inevitable.

THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below.

U.N. Ambassador Susan Rice said China and Russia were running the risk of suffering the same sort of international isolation as Assad because of their decision to block a U.N. Security Council vote embracing an Arab League solution for the Syrian crisis.

Rice said she thinks both Moscow and Beijing "will come to regret" their votes Saturday against the Arab League-sponsored resolution aimed at moving Assad in the direction of a peaceful transition to democracy in his violence-wracked country.

Rice told "CBS This Morning" she shares Secretary of State Hillary Rodham Clinton's view that the failed vote in the Security Council was a "travesty" and said the United States will continue to step up pressure for Assad to step aside.

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