The United States House of Representatives has passed a resolution to rein in President Donald Trump’s powers to attack Iran without congressional authorisation.

Four Republicans joined Democrats to pass the bill in a vote of 215 to 208 on Wednesday in Washington, DC.

While the resolution is unlikely to become law, it represents a stark rebuke against Trump’s decision to join Israel in attacking Iran on February 28, launching an ongoing conflict that will reach its 100th day on Saturday.

Trump did not seek congressional approval for the war, which he has attempted to label as a “skirmish” or a “short-term excursion”.

The Republican leader’s repeated use of military force abroad has frustrated some leaders in Congress, a body which the Constitution solely imbued with the power to declare war.

Wednesday’s vote marked the fourth time this year that the House has voted on a war powers resolution to force Trump to seek congressional backing for his military actions against Iran.

It is the first time, however, that the resolution has been successful in the House. Its passage comes after a political manoeuvre that some interpreted as a Republican effort to scuttle the bill.

A divide among Republicans

A vote on the war powers resolution was expected on May 21, the eve of Congress’s Memorial Day recess.

But the vote was cancelled, despite indications that the resolution would succeed with Republican support. House Speaker Mike Johnson, a Republican and close Trump ally, chose to adjourn the chamber early.

The resolution, however, was picked up again after the recess. In Wednesday’s vote, Tom Barrett of Michigan, Warren Davidson of Ohio, Brian Fitzpatrick of Pennsylvania and Thomas Massie of Kentucky splintered away from the Republican establishment to pass the bill.

Massie, whose re-election bid Trump actively campaigned against, marked the occasion with a message on social media.

“The Iran War Powers Resolution that I cosponsored (opposing the war) just passed the House of Representatives,” Massie wrote. “The People’s House is sending a message: end this war.”

Massie will not be returning to Congress next year. He was defeated last month in his local Republican Party primary by a Trump-backed opponent, Ed Gallrein.

Barrett, whose House seat is vulnerable to a Democratic takeover in November’s midterms, explained his vote by arguing that Trump had exceeded his mandate.

“Congress has the exclusive authority under the Constitution to declare war and authorize the use of force. The War Powers Act of 1973 delegates some of that authority to the president for a limited period of time,” Barrett, an army veteran, wrote.

“That authority has expired, and my support of this resolution tonight is consistent with my belief that it is time for Congress to decide the scope of the mission and the appropriate limits on the use of force in Iran.”

Democrats call on Senate to act

While Trump’s war on Iran has divided House Republicans, the chamber’s Democrats were unanimous in their backing of the war powers resolution. After the vote, several urged their colleagues in the Senate to swiftly pass the measure.

“We passed an Iran War Powers Resolution in the House to rein in Trump and end his unauthorized, reckless war,” Representative Ayanna Pressley, a progressive from Massachusetts, wrote on social media. “The Senate must immediately follow suit and act to end this war.”

Representative Shontel Brown of Ohio, meanwhile, underscored the constitutional issues raised by Trump’s war, as well as its cost.

“Congress holds the power to declare war—not the executive branch,” she said in a post. “After months of chaos, higher costs, and wasted resources, it is time to end Trump’s costly war in Iran NOW.”

The war on Iran has been costly for the US, with the Pentagon estimating in May that $29bn had been spent so far.

Some analysts consider this an undercount, though. In April, a public finance expert at Harvard University projected that the price tag could soar to more than $1 trillion.

There are also concerns that the war has cost the US in terms of military preparedness.

The Center for Strategic and International Studies, a US-based research institute, issued a report in April warning that certain critical munitions have run low, with the number used outstripping the number of anticipated replacements.

They include Tomahawk missiles, Terminal High Altitude Area Defense systems (THAADs) and Precision Strike missiles (PrSMs).

Public backlash growing

US voters broadly disapprove of the US-Israel war against Iran. A poll last month from the Marist Institute for Public Opinion found that 60 percent of US citizens disapprove of Trump’s approach to the war, a jump from 54 percent in March.

The increase was even seen among Republicans. While 15 percent disapproved of Trump’s handling of the war in March, the number has since increased to 22 percent.

Among US citizens overall, 61 percent found that the war had done “more harm than good”.

The growing disapproval reflects, in part, the economic backlash to the war, which has sent prices for fuel and other products like agricultural fertiliser skyrocketing.

The Trump administration has also faced criticism for the unprovoked nature of the February 28 attack, though the president and his allies have argued the war was necessary to prevent Iran from obtaining a nuclear weapon.

More than 3,400 people have died in Iran during the war. At least 13 US soldiers have also been killed in the conflict, which spilled into nearby countries, with deaths reported across the region.

Wednesday’s House war powers resolution now proceeds to the Senate, which passed a similar bill in May.

But it faces an uphill battle overall, as Trump is likely to veto any attempt to curtail his military powers.

Only a bill passed with a two-thirds majority in both the House and Senate can overcome a presidential veto. So far, neither the Senate’s version, nor the House’s, has breached that threshold.