The US Senate rejected a resolution on Wednesday to rein in President Donald Trump's handling of the Iran war, in an apparent U-turn following pressure from the Republican leader.

The move came just one day after the Senate voted 50-48 to pass a resolution calling for an end to the Iran war, delivering a rebuke to the White House as it seeks to negotiate a lasting deal with Tehran.

The legislation is seen as largely symbolic and has little chance of curbing executive authority, as the president has the constitutional power of veto.

Trump slammed the Tuesday vote as "poorly timed and meaningless," saying that it made his job more difficult.

US media reported that the president lashed out at Republican lawmakers during a closed-door lunch on Capitol Hill on Wednesday.

Trump "was mad as a murder hornet," Senator John Kennedy told the New York Times.

Other attendees told the newspaper that Trump aired a long list of grievances and complaints.

Hours later, Republican Senators Rand Paul and Bill Cassidy, who had called for a check on the president's war on Iran, changed their stance in the late Wednesday vote to align with Trump, CNN reported.

The Wednesday resolution, which was defeated 50-47, did not nullify or change the outcome of Tuesday's vote.

Trump took a more positive view of Wednesday's result, writing on Truth Social: "This vote puts Iran on notice!"