Washington DC - The US Congress is scheduled to vote this week on motions seeking to curb President Donald Trump as he wages war against Iran, but the Republican majority will probably shield him.

Trump has sought to expand executive power drastically since returning to the White House in 2025, overshadowing the legislature.

So some lawmakers now want to reassert the role of Congress, which under the US constitution is the only body that can declare war.

"Trump has launched an unnecessary, idiotic, and illegal war against Iran," Senator Tim Kaine wrote on X shortly after the US and Israel began it overnight Friday into Saturday.

In late January, as a huge US military buildup in the Middle East rumbled on, Kaine introduced a bill designed to force Trump to obtain authorization from Congress to engage in any military conflict with Iran.

On Saturday, he urged Congress to return immediately from recess to take up his resolution, and a vote is expected this week.

Secretary of State Marco Rubio and Pentagon chief Pete Hegseth visited the Capitol on Monday to discuss the new Middle East war with administration officials.

"There was no imminent threat to the United States of America by the Iranians. There was a threat to Israel," Senator Mark Warner, the lead Democrat on the Senate Intelligence Committee, told reporters after the meeting.

"If we equate a threat to Israel as the equivalent of an imminent threat to the United States, then we are in uncharted territory," he said.

This issue of whether there was an imminent threat from Iran is at the heart of the debate over the war that Trump has now begun with Israel.

Although only Congress can declare war, a law dating from 1973 allows the president to launch a limited military intervention in response to an emergency situation created by an attack on the US.

At a news conference Monday, Hegseth used the word "war" to describe the conflict with Iran, not just a limited military intervention.

In a video broadcast in the middle of the night from Friday into Saturday to announce the start of major combat operations, Trump asserted that Iran posed an "imminent" threat to the US.

Daniel Shapiro, an analyst with the Atlantic Council, a think tank in Washington, said Trump failed to explain "the urgency or the imminent threat that required a war now."

It is typical for presidents and their senior advisors to make their case to the American people and define what they are trying to achieve, in addition to briefing Congress broadly, Shapiro added.

But Trump did not do any of this, he said.

The White House said Sunday that just before the attack started, it gave eight top congressional leaders formal notice of hostilities.

The 1973 War Powers Act states that Trump must now obtain permission from Congress if he wants to keep fighting beyond a 60-day limit.

Republican Congressman Thomas Massie, one of few in Trump's party who speaks out regularly to challenge him, condemned the Iran war on Saturday.

Massie said he would present a bill in the House of Representatives along with his Democratic colleague Ro Khanna to force a vote by Congress on the war with Iran, which could as soon as this week.

"The Constitution requires a vote, and your Representative needs to be on record as opposing or supporting this war," Massie wrote on X.

Most Republicans, who are against tying Trump's hands, are expected to vote against both of the bills.

And even if they pass, they would probably not survive a veto by Trump because overriding him requires a two-thirds majority in both chambers.