A Syrian rebel commander said on Thursday rare military exercises with U.S. Marines in southern Syria sent a strong message to Russia and Iran that the Americans and the rebels intend to stay and confront any threats to their presence.

Col. Muhanad al Talaa, commander of the Pentagon-backed Maghawir al Thawra group, told Reuters the eight days of drills that ended this week at the U.S. military outpost in Tanf were the first such exercises with live-fire air and ground assault, involving hundreds of U.S. troops and rebel fighters.

"These exercises have a big importance and have beefed up the defenses of the area and raised the combat capabilities and morale and that of civilians in the area," Talaa told Reuters by phone from Tanf, near Syria's borders with Jordan and Iraq.