“Idriss says and does the right things,” a second U.S. official told me. “We believe he is genuine. Are there concerns? Yes, but what are the options?”

The United States is already sending non-lethal equipment to Idriss and helping train his forces in Jordan. A big U.S. shipment of humanitarian assistance arrived Tuesday from Turkey at a warehouse in a liberated area in northern Syria, handsomely packaged in a wrapper bearing the crest of the Supreme Military Council.

More aid is on the way. Already promised are armor, night-vision goggles and other war-fighting gear. The administration is discussing sending weapons and ammunition, too, though an official cautioned Wednesday that even if Obama decides to send the weapons, he probably won’t include the shoulder-fired anti-aircraft missiles the rebels desperately want. On that, says one U.S. official, “there’s apprehension” and “anxiety” — not least that one of the missiles might someday be aimed at Israel’s Ben Gurion Airport.

Idriss’s biggest challenge will be to gain control over the Islamist fighters who have formed the backbone of the Free Syrian Army for nearly two years.