Republicans largely welcomed strikes launched Saturday by US forces and ally Israel against Iran but prominent Democrats condemned what they called an illegal aggression.

"Today, Iran is facing the severe consequences of its evil actions," including "terrorism," the murder of Americans and the regime's sustained nuclear ambitions, Speaker of the House of Representatives Mike Johnson said in a statement.

"We pray for the safety of our brave servicemembers and our allies involved in Operation Epic Fury," the top Republican in Congress added.

However, the top Democrat in the Senate, Minority Leader Chuck Schumer, demanded a briefing to Congress by the Trump administration.

"The American people do not want another endless and costly war in the Middle East when there are so many problems at home," he said.

Justified

For Senator Lindsey Graham, a longtime supporter of US military intervention against Iran, Donald Trump's speech "will go down in history as the catalyst for the most historic change in the Middle East in a thousand years."

"It will be violent, extensive and I believe, at the end of the day, successful," he added in a series of X posts. "The demise of the ayatollah's regime with American blood on its hands is necessary and more than justified."

"This is a bold, decisive act of strength by President Trump," hailed senior House Republican Tom Emmer.

Republicans including Intelligence Committee chairman Tom Cotton, pointed to multiple grievances against Iran, in particular the 1979 hostage crisis and the deadly Beirut bombing of 1983.

"Iran has waged war against the US for 47 years," Cotton posted on X. "The butcher's bill has finally come due for the ayatollahs."

Trump has near total control of his Republican Party and dissent is rare.

Congressman Thomas Massie broke ranks to say: "I am opposed to this war."

"This is not 'America First,'" Massie posted, referring to Trump's widely used campaign slogan.

The Republican stressed that when the House and Senate reconvene, he will work with Democrats to "force a congressional vote on war with Iran."

'Illegal' action

Democrats were largely united against the large-scale attack on Iran.

Senator Jack Reed, top Democrat on the Armed Services Committee, argued Trump "has thrust our nation into a major war with Iran -- one he never made a case for, never sought congressional authority for, and for which he has no endgame."

The administration "has left the American people in the dark about the true costs, risks, and duration of this conflict."

Senator Ed Markey slammed Trump's attack order as "illegal and unconstitutional."

Fellow Democratic Senator John Fetterman, among the first to react to the attack on Iran, praised the operation.

"President Trump has been willing to do what's right and necessary to produce real peace in the region," he posted.