With a U.S. attack on Syria on hold, Western-backed rebels said they feared they had lost their best chance of promptly ousting President Bashar al-Assad and sidelining Islamist extremists. …

“The revolution is dead. It was sold,” said Mohammad al-Daher, a commander in the rebels’ Western-backed Free Syrian Army. “People used to assume that Assad will be gone, no question. But I wouldn’t be surprised if the end result of these negotiations is that he remains as president and beyond that, turns into a national hero who saved his country.” …

Rebels based in the Damascus suburbs, counting on the U.S., had already adjusted their battle plans. Anticipating American airstrikes that in their view could help neutralize Mr. Assad’s air force, the rebels plotted to follow with an assault on the Syrian capital that, they hoped, would crack the regime, according to these rebels.

Those expectations—as with other rebel hopes for game-changing U.S. intervention over the course of the 2½-year conflict—appear to have been unrealistic. Mr. Obama raised the idea of U.S. military action as a way to punish the Assad government for using chemical weapons—not to help the rebels in the battle on the ground.