WASHINGTON (AP) — The Trump administration and its allies in Congress presented a shifting new justification Monday for the U.S. attack on Iran, with House Speaker Mike Johnson suggesting that the White House believed Israel was determined to act on its own, leaving the president with a “very difficult decision.”

The Republican was speaking late Monday after a classified briefing at the Capitol, the first for congressional leaders since the start of the war, a joint U.S.-Israel military campaign that killed Iran’s Supreme Leader Ayatollah Ali Khamenei and has quickly spiraled into a widening Middle East conflict. Hundreds have died, including at least six U.S. military service personnel.

Johnson said the attack on Iran was a “defensive operation” because Israel was ready to act against Iran, “with or without American support.” He said President Donald Trump and his team determined that Iran would immediately retaliate against U.S. personnel and assets.

“The commander in chief has said this is going to be an operation that is short in duration,” Johnson said. “We certainly hope that’s true.”

Operation Epic Fury was a defensive and decisive action taken to counter the imminent threat posed by Iran’s aggression toward American troops, citizens, installations, and assets.

Our intelligence confirmed that inaction would have resulted in dire consequences.

We… pic.twitter.com/ihRai0ycF1

— Speaker Mike Johnson (@SpeakerJohnson) March 3, 2026

The remarkable shift in the Trump administration’s stated rationale comes as the hostilities deepen and widen across the region. The president himself estimated the war could drag on for weeks. The administration plans to seek supplemental funds from Congress to support the military effort, lawmakers said, in stark contrast to the president’s America First campaign not to entangle the U.S. in actions abroad.

Secretary of State Marco Rubio said the “hardest hits are yet to come” as the U.S. is determined to continue attacking Iran for as long as it takes with an “even more punishing” next phase in the war.

Rubio described what was essentially a potentially ripple effect that he said posed an “imminent threat” to the U.S.

Rubio said that while the U.S. would like to see the Iranian people rise up and be rid of the regime, “that’s not the objective,” he said. “The objective of this mission is to make sure they don’t have these weapons that can threaten us and our allies in the region.”