Three American troops have been killed and 34 injured in a drone attack in Jordan.
Those killed in the attack were sleeping in a tent at a place called Tower 22 in northeast Jordan, near the Syria border, and some of those injured are being evacuated from the country.
US President Joe Biden said the attack was carried out by "radical Iran-backed militant groups" in Syria and Iraq on Saturday night.
"While we are still gathering the facts of this attack, we know it was carried out by radical Iran-backed militant groups operating in Syria and Iraq," he said in a statement.
The Pentagon has still not released details on the types of injuries sustained, but a US official said 34 personnel are being monitored for possible traumatic brain injuries - which is a common occurrence after a large blast.
An earlier statement from the US military had said 25 were injured in the attack.
It's the first time US troops have been killed in the region since war began in Gaza.
"We will carry on their commitment to fight terrorism," Mr Biden continued, referring to the "patriots" who died in the attack.
"And have no doubt - we will hold all those responsible to account at a time and in a manner of our choosing."
A spokesman for Jordan's government, however, said the attack did not happen on their soil and insisted it was in Syria. They said the attack did not result in the injury of any Jordanian border guards.
The US has long used Jordan - which neighbours Iraq, Israel, the Palestinian territory of the West Bank, Saudi Arabia and Syria - as a basing point, with about 3,000 troops typically stationed there.
Since the war in Gaza began, US troops in Iraq and Syria have faced drone and missile attacks on their bases, but this was the first time they've been attacked in Jordan.
While US officials are still working to identify the precise group responsible for the attack, they believe one of several Iranian-backed groups are responsible.
The identities of the military service members killed will be withheld for 24 hours until their next of kin have been informed, say US officials.
The attack is a major escalation in the Middle East, where war broke out after Palestinian Islamist group Hamas attacked Israel on 7 October, killing 1,200 and taking dozens to Gaza as hostages.
Israel's subsequent assault on Gaza has killed more than 26,000 Palestinians, according to the local health ministry.
While the US has maintained it is not at war in the region, it has - along with the UK - made strikes against targets of Yemen's Houthi groups, which have been attacking commercial vessels in the Red Sea.