WASHINGTON (Reuters) — President Donald Trump has authorized the U.S. military to respond to Wednesday’s rocket attack by Iran-backed militia in Iraq that killed two American troops and a British service member, the Pentagon said on Thursday.

Defence Secretary Mark Esper and Army General Mark Milley, chairman of the Joint Chiefs of Staff, stopped short of blaming Iran-backed Kataib Hezbollah or naming any specific militia. However, they were clear that they believe Iran backed the fighters who carried out the attack, and warned that all options were on the table. “I have spoken with the president. He’s given me the authority to do what we need to do, consistent with his guidance”, Esper told reporters at the Pentagon.

Asked if a U.S. response could include strikes inside Iran, Esper hinted that strikes against the militia itself were the priority:

I’m not going to take any option off the table right now, but we are focused on the group — groups — that we believe perpetrated this in Iraq, as the immediate [focus].

Trump told reporters at the White House it was not “fully determined it was Iran” and declined to say what the United States might do. “We’ll see what the response is”, he said.

The United States has repeatedly and publicly warned that killing Americans overseas constituted a red line that would trigger a U.S. response.