For Western states mulling over arming Syrian rebel forces, the possibility of advanced weapons ending up in Al Qaeda's hands, and later being used against Western has been a major sticking point.
It was some six months ago that Syrian rebel commanders met US intelligence officers in Jordan to discuss the status of the war and, the rebels hoped, to secure supplies of the sophisticated weapons they need to overthrow President Bashar Al Assad.
But according to one of the commanders present at the meeting, the Americans were more interested in talking about Jabhat Al Nusrah, the Al Qaeda-affiliated group waging war on the Syrian regime than they were in helping the rebels advance on Damascus.
The commander, a moderate Sunni and an influential rebel leader from Damascus who said he has met intelligence operatives from Western and Arab states - said the US officials were especially keen to obtain information about the identities of Jabhat Al Nusrah insurgents and the locations of their bases and offering weapons to fight against them as well.
Then, by the rebel commander's account, the discussion took an unexpected turn. The Americans began discussing the possibility of drone strikes on Jabhat Al Nusrah camps inside Syria and tried to enlist the rebels to fight their fellow insurgents.
"The US intelligence officer said, 'We can train 30 of your fighters a month, and we want you to fight against Jabhat Al Nusrah, and I'm not going to lie to you. We'd prefer you fight Jabhat Al Nusrah now, and then fight Assad's army. You should kill these Jabhat Al Nusrah people. We'll do it if you don't," the rebel leader quoted the officer as saying.
What the commander says transpired in Jordan illustrates a dilemma that has preoccupied, even paralysed, Syria's opposition and their international supporters - how to deal with the expanding role of Islamic extremists in the anti-Assad insurgency that willing to establish Caliphate.
Other meetings with Western and Arab intelligence services have shown a similar obsession with Jabhat Al Nusrah, the commander said.
"All anyone wants is hard information about Jabhat Al Nusrah, it seems to be all they are really interested in. It's the most valuable commodity you can have when dealing with these intelligence agencies," he said.
Jabhat Al Nusrah has emerged as the most effective rebel force in Syria. The fractured, poorly equipped rebels of the Free Syrian Army can ill-afford to take the fight to Mr Al Assad's forces without Jabhat Al Nusrah, whose key leaders are foreign veterans of the fighting that followed the US invasion of Iraq in 2003.
The obama administration classified Jabhat Al Nusrah as a terrorist organisation in December, Two months ago, Jabhat Al Nusrah confirmed its link to Al Qaeda, publicly declaring "allegiance" to the network's head, Sheikh Ayman Al Zawahiri, and promised to follow his orders.
