'We shall respond': Biden warns militants after 3 U.S. troops killed in Jordan

Top U.S. leaders issued a warning on Sunday to Iran-backed militants, a day after a drone attack killed three U.S. troops in Jordan, dramatically escalating the situation in the Middle East.

“We had a tough day last night in the Middle East. We lost three brave souls in an attack on one of our bases," President Joe Biden said in South Carolina.

He then asked for a moment of silence and added: “And we shall respond.”

Defense Secretary Lloyd Austin said he was "outraged and deeply saddened" by the deaths and vowed that the strike would not go unanswered.

"Iran-backed militias are responsible for these continued attacks on U.S. forces, and we will respond at a time and place of our choosing," he said in a statement. "The president and I will not tolerate attacks on American forces, and we will take all necessary actions to defend the United States, our troops, and our interests.”

Three U.S. service members were killed and 25 more were wounded Saturday night in the drone attack. The assault marks the first time American troops have been killed in months of drone and missile attacks on U.S. forces in Iraq, Syria, and now Jordan that began not long after Hamas militants killed 1,200 Israelis on Oct. 7. The hit impacted the base's living quarters, according to a U.S. official, who like others was granted anonymity to speak about a developing situation.

A second U.S. official said the three service members were from the Army. Response options are being drawn up "as we speak," a third U.S. official said.

The base, known as Tower 22, is a small outpost attached to the Rukban refugee camp, near the Iraq-Syria border. U.S. special operations troops have used the location to cross into Syria to help fight the Islamic State. It's also just a few kilometers away from Syria's al-Tanf Garrison, which has been targeted dozens of times by Iran-backed proxies since October.

A White House official said the president was briefed Sunday morning on the attack by Austin, national security adviser Jake Sullivan, and Principal Deputy National Security Advisor Jon Finer.

In a recorded interview posted Sunday morning on ABC’s “This Week,” Joint Chiefs Chair Gen. C.Q. Brown said the U.S. does not want the conflict in the Middle East to continue to broaden.

“The goal is to deter them and we don’t want to go down a path of greater escalation that drives to a much broader conflict within the region,” he said.

The attack "has to be responded to with significant force, more force than we have used to date," said Mick Mulroy, former Defense Department official, retired CIA paramilitary officer and Marine. "Not only should the group that launched this attack be targeted, but the Iranian IRGC Quds Force should as well."

Several prominent Republican senators on Sunday also called on the administration to strike inside Iran.

American and British warships have also been busy shooting down drones and ballistic missiles by Iranian-backed Houthi militants in Yemen. Several commercial ships have been struck, disrupting global trade routes in the Red Sea.

Since October, Iran proxies have hit U.S. and allied forces in the Middle East 158 times, though so far they have caused only minor injuries and damage to infrastructure.

The Tower 22 base has seen action before. On Oct. 23, Iran-backed militants in Syria launched multiple one-way attack drones close to al-Tanf Garrison, POLITICO reported previously. Coalition forces at Tower 22 took down the drones, which fell on the Syrian side of the border.

Most U.S. troops in Syria are located in the northeast of the country, but a small number are stationed far south at al-Tanf Garrison. In addition to helping fight ISIS, those troops are also there to put pressure on Iran and the Syrian regime by disrupting transit along the Baghdad-Damascus highway.

Eugene Daniels and Alexander Ward contributed to this report.