Continued from page 1

“I obviously don’t agree with that analysis,” said Aaron Zelin, a scholar at the Washington Institute for Near East Peace who penned a paper examining the extremist strands within Syria’s opposition forces. “I think it’s somewhat naive because all the key offenses in Syria and all the key liberations of cities during 2013 have been led by Islamist forces.”

Mr. McCain and Mr. Kerry have “a more optimistic view of things and they’re more idealistic about the Islamist elements within the opposition that what the reality is on the ground,” Mr. Zelin said. “Even though they would probably say they are moderate Islamists, they’re fighting alongside extremist groups and it’s not as if there’s this clear distinction between them militarily speaking. These guys are working together in operations.”

Official U.S. intelligence community assessments of the Syrian opposition remain closely guarded.

One U.S. official told The Times that “most of the groups battling against Assad are composed of Islamist fighters, but only a minority could accurately be characterized as extremist.”

During a panel discussion last week at the Brookings Institution, Bruce Riedel, a former career analyst for the CIA, warned that “if we tilt the playing field in Syria against the Assad regime, inevitably, that helps al Qaeda.”

Mr. Riedel also said that claims about the level of extremists in the fight in Syria should be read with skepticism. “Anyone who tells you there are 5,000 al Qaeda fighters in Syria — your alarm bell should go off,” he said. “How do they know things like that? It’s doubtful that al Qaeda knows how many people it has in Syria today.”

Other analysts have been quick to rebut claims that extremists such as the al Qaeda-connected Jabhat al-Nusra are marginal players in Syria and that U.S. bombing will not help them.

“I’d only be in favor of these strikes if they simultaneously strike at the al-Nusra Front rebels,” Bart Bechtel, a former CIA officer in the region, told The Washington Times. “Those are the hard-line Islamists who are killing Christians. Any damage to the Assad regime is gong to benefit any opposition.”

Rowan Scarborough and Shaun Waterman contributed to this report.