Syria's foreign ministry on Thursday accused the United States of inciting "armed groups" into acts of violence targeting the country's military.
"Comments by American officials, notably (US State Department spokesman) Mark Toner, are striking proof that the United States encourages armed groups to commit violence against the Syrian Arab army," a ministry statement said.
The accusation came as America's ambassador in Syria, Robert Ford, was reportedly blocked inside a building by pro-regime demonstrators after he arrived at the office in Damascus of opposition member Hassan Abdelazim.
According to Abdelazim, "nearly 100 protesters" tried to break into his office as the US envoy arrived for a meeting.
"They were protesting in the street and at the entrance to the building. They tried to break down the door of my office, but didn't succeed," Abdelazim told AFP.
"As soon as the ambassador came in at around 11:00 am (0800 GMT), we heard a noise outside and hostile slogans being chanted. The demonstrators tried to attack the office," he added.
Ambassador Ford was still in the office two hours later waiting for security forces to arrive so he could leave under their protection, Abdelazim said.
Toner on Tuesday, in answer to a question by a reporter, said in Washington it came as no surprise that some arms are being sent to Syria's opposition.
"Well, look, I think it’s not surprising, given the level of violence over the past months, that we’re now seeing members of the military -- or, rather, members of the opposition -- begin to turn violent, or, rather, begin to use violence against the military as an act of self-preservation," Toner said.
"I would say that the opposition’s shown extraordinary restraint in the face of the regime’s brutality and demanding their rights through peaceful unarmed demonstrations," he added.
"It goes without saying that the longer the regime continues to repress, kill, and jail these peaceful activists, the more likely that this peaceful movement’s going to become violent."