At least 34 personnel were being evaluated for possible traumatic brain injury, a U.S. official told Reuters, speaking on condition of anonymity. Two different officials said some wounded U.S. forces were medically evacuated from the base for further treatment.

The Islamic Resistance in Iraq, an umbrella organization of hardline Iran-backed militant groups, claimed attacks on three bases, including one on the Jordan-Syria border.

"This is the tipping point," said James. "It's not necessarily a tipping point into uncontrolled escalation between the United States and Iran, but it's another very dangerous step because as I say, the U.S. will have to respond even more strongly than it's done to previous attacks."