Washington — Three American service members were killed and dozens more were injured in an unmanned aerial drone attack on a base in Jordan on Sunday, President Biden and the U.S. military said.

In a statement, the president blamed the attack on "radical Iran-backed militant groups operating in Syria and Iraq," and said the U.S. "will hold all those responsible to account at a time and in a manner our choosing."

Mr. Biden said the attack happened at a base in northeast Jordan, a U.S. ally, close to the border with Syria. A U.S. official said the attack occurred at an outpost known as Tower 22, where roughly 350 U.S. Army and Air Force personnel are deployed, according to the Department of Defense.

U.S. Central Command, which oversees forces in the Middle East, initially put the number of injured at 25, but two U.S. officials soon said that figure had risen to more than 30. CENTCOM confirmed later Sunday night that at least 34 had been injured. Eight of the wounded service members had to be evacuated — some were in critical condition but all were stable, a defense official told CBS News.

The killed and injured troops were in their sleeping quarters on the base when the drone strike took place in the pre-dawn hours.  

CENTCOM said the identities of those killed would be withheld for 24 hours after their families had been notified. 

The White House said the president was briefed on the attack Sunday morning and met with top aides, including Defense Secretary Lloyd Austin and Secretary of State Antony Blinken, again in the afternoon.

"I want to point out that we had a tough day last night in the Middle East," Mr. Biden said Sunday afternoon at a lunch event in South Carolina. "We lost three brave soldiers in an attack on one of our bases. And I'm asking for a moment of silence for all three of our fallen soldiers."

"And we shall respond," Mr. Biden added.

The strike was believed to be the deadliest attack on U.S. service members since 13 Americans were killed in a suicide bombing in Kabul as the U.S. pulled out of Afghanistan in 2021. 

The drone strike comes as tensions between the U.S. and Iran's proxies in the region have soared to precarious heights in recent weeks, raising the risk of Israel's war with Iranian-backed Hamas in Gaza erupting into a broader regional conflict.

Yemen's Iranian-backed Houthi rebels began attacking shipping vessels in the Red Sea in October to protest the war in Gaza. The U.S. and its allies started launching airstrikes against Houthi targets in Yemen earlier this month, hoping to put an end to the shipping attacks. On Friday, Houthi militants launched a missile at the USS Carney, the first time the group had targeted a U.S. warship. The destroyer shot the missile down without any injuries. 

The week before, the U.S. military said two Navy SEALs were lost at sea after they went overboard while trying to board an Iranian vessel that was delivering "advanced conventional weapons" to the Houthi rebels.

Congressional Republicans reacted angrily to news of the attack, calling on the Biden administration to retaliate against Iran. House Speaker Mike Johnson said the administration "must send a crystal clear message across the globe that attacks on our troops will not be tolerated." Sen. Lindsey Graham of South Carolina, a prominent GOP defense hawk, said the U.S. should strike "targets of significance" inside Iran itself to deter future attacks.

"Hit Iran now," Graham said. "Hit them hard."

A Jordanian government spokesperson condemned Sunday's attack and said there were no casualties among the Jordanian Armed Forces.

"Jordan will continue to counter terrorism and the smuggling of drugs and weapons across the Syrian border into Jordan," the spokesperson said, referring to the drug fenethylline, sold as "Captagon," which is an amphetamine used by terror groups in the Middle East and largely produced by Syria's Assad regime.

Margaret Brennan, David Martin, Nancy Cordes and Christina Ruffini contributed reporting.

Stefan Becket

Stefan Becket is assistant managing editor, digital politics, for CBSNews.com. He helps oversee a team covering the White House, Congress, the Supreme Court, immigration and federal law enforcement.

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