The United States closed its embassy in Syria and pulled out its remaining diplomatic staff on Monday after Damascus refused to address security concerns raised by the State Department.
"The government is getting stretched beyond its ability to control the various elements of violence in the country," one senior official told CNN.
"This is a decision we never take likely. Our embassies are a very important part of our diplomacy around the world."
According to the official the last 15 employees, including Ambassador Robert Ford, had been taken to Jordan by convoy on Monday. Two other employees departed by commercial air last week.
Most of the staff were evacuated earlier in the year, and the diplomatic team was further reduced in December.
Syrian officials were notified about the decision to pull the staff and shutter the embassy only after the staff had safety arrived in Jordan.
The decision came in the wake of last month's deadly car bombings at the offices of two Syrian security branches in Damascus, which officials believe bear the hallmarks of al Qaeda.
However, US officials were less concerned about Al Qaeda's bombs than they were violent mobs who might seek to overrun the embassy and lynch its staff.
"I'm more concerned about a suicide bombing than I am a mob at the embassy," one senior official told CNN. "There is a shadow of instability across the country."
Officials say Damascus has declined numerous requests to beef up security for the centrally located embassy and create a more robust perimeter with barriers.
Poland will serve as the US protecting power in Syria and will assist any US citizens remaining in Syria who face trouble.
However, officials stressed the move does not mean the U.S. is breaking diplomatic ties with Damascus and that formal relations will remain intact.
Officials said Ford and his staff would continue work from the State Department's Washington headquarters until the embassy can be reopened.