The US Congress has delivered a rare and historic rebuke to President Donald Trump over the conflict with Iran, after the Republican-controlled Senate approved a war powers resolution directing him to halt US military action unless he obtains congressional authorisation.

The measure passed the Senate on Tuesday by 50 votes to 48, with four Republican senators joining Democrats in support: Rand Paul of Kentucky, Susan Collins of Maine, Lisa Murkowski of Alaska and Bill Cassidy of Louisiana. Democratic Senator John Fetterman of Pennsylvania was the only member of his party to vote against it.

The same resolution had already passed the Republican-controlled House of Representatives earlier this month by 215 votes to 208, with four Republicans joining every Democrat in favour.

The vote is politically significant because it marks the first time since the War Powers Resolution was enacted in 1973 that both chambers of Congress have approved a concurrent resolution directing a president to end a military action. However, the measure is largely symbolic. As a concurrent resolution, it expresses the position of Congress but is not sent to the president for signature and does not carry the force of law.

The resolution directs Trump to remove US forces from hostilities against Iran unless Congress declares war or gives formal authorisation for military action, except in cases involving an imminent attack on the United States.

The vote comes amid growing unease in Washington over the Iran conflict, which began with US-Israeli strikes on February 28 and has become increasingly unpopular with the American public. The Trump administration has argued that an April ceasefire reset the legal clock under the War Powers Resolution, which requires congressional approval for military operations lasting more than 60 days, with a possible 30-day extension on national security grounds.

The White House dismissed the measure, saying there were no active hostilities from which US forces needed to be withdrawn after the ceasefire agreement reached with Iran. Officials also noted that the resolution passed while two Republican senators, Mitch McConnell and Dave McCormick, were absent.

Trump criticised the Senate vote on Truth Social, calling it “poorly timed and meaningless” and accusing senators of making his job more difficult while he sought to push forward an agreement with Iran.

The vote nevertheless exposes divisions inside the Republican Party ahead of November’s midterm elections, when control of both chambers of Congress will be at stake. It also increases political pressure on the White House as lawmakers question the cost, legality and duration of US military involvement in Iran.

The Senate action came on the same day the Pentagon asked Congress for about $80 billion in additional funding, most of it related to the Iran conflict.