White House promises retaliation against Iran proxy group: 'The first thing you see won't be the last'

White House national security spokesman John Kirby reiterated Wednesday that the U.S. will respond after three American soldiers were killed in a drone attack by an Iran-backed proxy group.

President Biden on Tuesday blamed Iran for providing weapons to the militant groups that perpetuated the attack and said he had decided how to respond but did not offer further details. But with no public action in the days since the attack, a reporter asked Kirby whether the White House had missed an opportunity to signal resolve. 

"I think we signal resolve pretty well. And as I said the other day, we'll respond on our own time, on our own schedule, and we'll do that," Kirby said at the daily White House press briefing.

"The first thing you see won't be the last," he added.

DRONE FROM IRAN PROXY EVADED US DEFENSES BECAUSE IT WAS MISTAKEN FOR US DRONE: OFFICIAL

National Security Council spokesman John Kirby speaks during the daily briefing at the White House in Washington, D.C., on Jan. 31, 2024. (Mandel Ngan/AFP via Getty Images)

Kirby identified the Islamic Resistance in Iraq, a loose coalition of Iran-backed militant groups, as the perpetrators of the attack in Jordan on Sunday.  

The Pentagon identified those killed in the attack as Sgt. William Jerome Rivers, 46, of Carrollton, Georgia; Spc. Kennedy Ladon Sanders, 24, of Waycross, Georgia; and Spc. Breonna Alexsondria Moffett, 23, of Savannah, Georgia. The Army Reserve announced on Tuesday that it had posthumously promoted Sanders and Moffett to the rank of sergeant.

In addition to those killed, at least 34 service members were injured, including at least eight personnel whose injuries warranted an evacuation from Jordan to higher-level care, though they were believed to be in stable condition. 

Kirby remained tight-lipped about the details of the planned U.S. response.

WHO IS THE IRAN-BACKED COALITION ISLAMIC RESISTANCE IN IRAQ, RESPONSIBLE FOR THE DEADLY DRONE STRIKE ON US TROOPS? 

A map depicting the location of Tower 22 in northeast Jordan, near the borders of Syria and Iraq. (Fox News)

"I'll just say that we're confident in the planning and we're confident in the response that we – what we plan to undertake," he told reporters. 

He did say that the president's decision to move forward was based on discussions with his national security team and that it would not be limited to a "one-off." 

Kirby said "this will be a response over time" and that Biden will "continue to weigh options ahead of him, continue to ask tough questions, continue to talk to his national security team as things go forward." 

BIDEN SAYS HE'S DECIDED ON RESPONSE TO IRANIAN-BACKED MILITIA ATTACK THAT KILLED 3 US SOLDIERS IN JORDAN

The U.S. military base in northeastern Jordan known as Tower 22 is seen in this satellite photograph, taken on Oct. 12, 2023. Three American soldiers were killed and others were wounded in a drone strike on Jan. 28, 2024. (Planet Labs PBC via AP)

There have been a total of 166 attacks on U.S. military installations since Oct. 18, including 67 in Iraq, 98 in Syria and now one in Jordan, a U.S. military official said. 

Meanwhile, Houthi militants based in Yemen have been firing upon commercial vessels in the Red Sea, prompting retaliatory strikes from the U.S. and its allies.

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On Tuesday, Al-Asad Air Base in western Iraq was targeted again by a single rocket, but there was no damage and no injuries in that attack, a U.S. military official said.

The three soldiers killed in the Jordan strike were the first U.S. military fatalities in the Middle East from enemy fire since the war between Israel and Hamas broke out. One contractor has also died as the result of a heart attack after a strike on Al-Asad in December. Two U.S. Navy SEALs recently went missing during a mission in the Red Sea and have since been declared dead.

Fox News Digital's Bradford Betz and The Associated Press contributed to this report.