US officials said there had been credible threats against Robert Ford's life and accused the Syrian government of failing in its international obligations to protect him. Ford, who is back in Washington after leaving Damascus at the weekend, angered the Syrian government by aligning himself with Arab spring protesters.
Defying a travel ban on diplomats travelling outside Syria's capital, he regularly spoke to leaders of the opposition to President Bashar al-Assad. Unconventional by US diplomatic standards in his outspokenness, Ford communicated directly with the protesters through Twitter and Facebook.
The US state department stressed that Ford's return home did not amount to a formal breakdown in relations and that his deputy, Haynes Mahoney, would remain in Damascus to carry out his duties.
Mark Toner, a state department spokesman, said: "Ambassador Robert Ford was brought back to Washington as a result of credible threats against his personal safety in Syria. At this point, we can't say when he will return to Syria. It will depend on our assessment of Syrian regime-led incitement and the security situation on the ground."
A US embassy official in Damascus said: "Ambassador Ford's presence is a benefit to our mission in Syria as he has worked diligently to deliver our message and be our eyes on the ground. This decision was based solely on the need to ensure his safety, a matter we take extremely seriously."
Ford had been in the job less than a year. The US had recalled its ambassador to Syria in 2005 in protest against the alleged involvement of Damascus in the assassination of the Lebanese prime minister Rafiq Hariri. Ford's arrival in Damascus in January coincided with the US push to improve relations.
He wrote on Facebook last month: "This isn't about Western military intervention. This isn't about oil (many governments have banned its import). This isn't about Israel or the West wanting to dominate the Arab world (an old, discredited government line). This is about basic political freedoms from the United Nations' human rights charter – signed by Syria, don't forget – which calls for freedom of speech and freedom of peaceful assembly."
Ford has been repeatedly criticised by Syria's state-run media. The decision to leave on Saturday came after the appearance of more articles critical of him.
But in a speech in Jordan on Sunday, Senator John McCain, one of the Republican's leading foreign affairs specialists, said there were growing calls from the opposition in Syria for some kind of foreign military intervention.
McCain added: "Now that military operations in Libya are ending, there will be renewed focus on what practical military options might be considered to protect civilian lives in Syria. The Assad regime should not assume that it can get away with mass murder. Gaddafi made that mistake, and it cost him everything."