THREE American service members have been killed and “many” wounded in a drone strike in Jordan, US president Joe Biden has said.

He attributed the attack to Iran-backed militia groups in a statement on Sunday.

They were the first US deaths in months of strikes against American forces across the Middle East by Iranian-backed militias amid the war in Gaza, increasing the risk of escalation.

Biden said the United States “will hold all those responsible to account at a time and in a manner our choosing”.

In a statement reported by Sky News, Biden blamed the attacks on "radical Iran-backed militant groups" in Syria and Iraq". 

He said: "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.

"We will carry on their commitment to fight terrorism.

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"And have no doubt - we will hold all those responsible to account at a time and in a manner of our choosing."

The Associated Press reported there was no immediate reaction from Jordan, which borders Iraq, Israel, the Palestinian territory of the West Bank, Saudi Arabia and Syria.

US troops have long used Jordan as a base. Some 3,000 American troops typically are stationed in Jordan.

Since Israel’s war on Hamas in the Gaza Strip began, US troops in Iraq and Syria have faced drone and missile attacks on their bases.

The attack on Jordan marks the first targeting of American troops in Jordan during the war.

Biden was briefed on the attack on Sunday, White House press secretary Karine Jean-Pierre said.