The US has withdrawn it's ambassador from Syria over fears for his safety in the face of what officials said was a growing campaign of incitement against him being orchestrated by the regime.
The Syrian government quickly ordered home its envoy to the United States, raising the diplomatic stakes.
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 Damascus, he has regularly spoken to leaders of the opposition to President Bashar al-Assad. Unconventional by American diplomatic standards in his outspokeness, he communicated directly with the protesters through Twitter and Facebook.
The tit-for-tat withdrawals add to tensions between Damascus and Washington, which has called on Assad to stop using violence against peaceful protesters and step down from power.
The state department stressed that Ford's return home did not amount to a formal breakdown in relations and that Ford's deputy, Haynes Mahoney, would remain in Damascus to carry out Ford's duties.
Mark Toner, the state department spokesman, accused Syria of incitement. "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," Toner said.