Arab diplomatic sources said the Hashemite kingdom was hosting the training of thousands of Islamist rebels in the war against Syrian President Bashar Assad. They said the rebels, trained and equipped by Saudi Arabia and the United States, were moving into the southern suburbs around Damascus as well as the southern city of Dera.

“They are now considered to be the best-equipped rebel force in southern Syria,” a diplomat said.

Jordan has dismissed reports of training and deploying Sunni rebels. But the sources said the flow of trained rebels from Jordan to Syria intensified over the last month and reached the Eastern Ghouta region outside Damascus in an attempt to break the siege of the Syrian Army and its Hizbullah ally.

The sources said the Jordanian-origin force was being commanded by Saudi intelligence with guidance from the CIA. They said most of the militias were operating under the auspices of the Western-backed Free Syrian Army and played a role in the rebel offensive around Damascus in late November.

Syria has expressed anger at the flow of rebels from Jordan. The sources said the Assad regime has relayed veiled threats of retaliation.

“There have been visits and discussions between the two countries,” Syrian Deputy Foreign Minister Faisal Meqdad said.

In an interview with the pro-Assad Al Mayadeen satellite channel, Meqdad said Jordan was being forced by Saudi Arabia to host the Syrian rebels. The Syrian deputy minister warned of what he termed a “terrorist” backlash against the Hashemite kingdom.

Oraib Al Rantawi, the director of the Al Quds Center for Political Studies, acknowledged that Jordan’s allies were supporting the Syrian rebels. Still, Al Rantawi, regarded as close to the Hashemite leadership, said Jordan intensified efforts to stop the flow of fighters to Syria.

But Al Rantawi said Jordan could do more to stop FSA and the Saudi-sponsored Islamic Army, reported to have a presence in the kingdom. He said Jordan faces a choice of losing Saudi support or risking an Al Qaida backlash.

“We appreciate the fact that it is difficult to walk in a minefield without any maps,” Al Rantawi said. “We understand the attempts to postpone the moment when we have to choose between options, the sweetest of which is still very bitter. But we are now approaching the moment of truth and decision.”