The Republican-led US House of Representatives backed a resolution on Thursday directing President Donald Trump to halt US military action against Iran unless he obtains Congress' approval, but the Senate voted hours later to block a separate, similar measure.
The House vote, the latest rebuke of Trump from Congress, was 214-208 in favour of the war powers resolution as four Republicans joined Democrats in voting for it.
But the Senate voted 49 to 47 to block its own war powers measure within hours of the House vote.
The House resolution, introduced by Representative Pramila Jayapal, a Washington Democrat, directed Trump "to remove the use of United States Armed Forces from hostilities" against Iran unless Congress authorises it. However, it was largely symbolic.
Lawmakers have passed similar resolutions repeatedly in recent months, but they have not led to a cessation of the war.
The four House Republicans who voted in favour were Tom Barrett of Michigan, Brian Fitzpatrick of Pennsylvania, Warren Davidson of Ohio and Thomas Massie of Kentucky.
Growing frustration
In the Senate procedural vote, Republican Susan Collins of Maine voted with Democrats in favour of the resolution and Democrat John Fetterman of Pennsylvania voted with Republicans against it. Four Senators did not vote.
Trump's Republicans hold slim majorities in the House and Senate.
The votes reflected growing frustration among lawmakers of both parties about a conflict that Trump pitched as a quick, focused effort that would trigger Iran's capitulation but instead has become a morass for the United States.
Trump recently announced a ramp-up in attacks on Iran, and the deaths of more US service members.
Trump on Thursday promised "major military punishment" for Iran and its Houthi allies, after the Yemeni rebels struck two Saudi oil tankers in the Red Sea, extending the war in the Middle East to a second major shipping chokepoint.
Additionally, two weeks since the effective collapse of an interim truce meant to end the war, the US military launched another nightly round of air strikes on Iran, prompting Iran to fire at US bases in neighbouring countries.
