Washington: The U.S. Senate on Tuesday took a major step toward advancing a resolution aimed at ending military involvement in Iran, dealing a political setback to President Donald Trump.

The War Powers Resolution moved forward with a narrow 50–47 procedural vote after several Republican senators either broke ranks or declined to vote. Although the measure still faces significant hurdles before becoming law, its progress signals growing concern in Congress over continued military engagement with Iran.

Rising fuel prices, increasing inflation and Trump’s declining approval ratings ahead of the November midterm elections have reportedly added pressure on Republican lawmakers. The development also highlights widening tensions between the White House and Senate Republicans.

Louisiana Republican Senator Bill Cassidy, who recently lost a primary election after facing strong opposition from Trump, voted to advance the resolution despite previously opposing it.

North Carolina Senator Thom Tillis did not vote, while Texas Senator John Cornyn also abstained after Trump unexpectedly withdrew support for him earlier Tuesday. Alabama Senator Tommy Tuberville likewise did not participate in the vote.

Meanwhile, Republican senators Lisa Murkowski, Susan Collins and Rand Paul joined Democrats in supporting the resolution.

Democratic Senator Tim Kaine, who introduced the measure, argued that the Trump administration had exceeded the legal 60 day limit for military action abroad without congressional authorization.

“The administration is unwilling to show Congress the legal basis for this war,” Kaine said before the vote, calling the situation “a flashing red light.”

Trump had claimed in a May 1 letter to lawmakers that hostile actions against Iran had already ended. However, during a Senate hearing on May 13, Murkowski challenged Defense Secretary Pete Hegseth, saying the continued deployment of 15,000 troops, more than 20 warships and an active naval blockade suggested hostilities were still ongoing.

The resolution is viewed as a victory for Democrats, who argue that under the U.S. Constitution, the authority to declare war rests with Congress, not solely with the president.

Under U.S. law, presidents may conduct military operations for only 60 days without congressional approval, after which they must either end the operation, seek authorization from Congress or request an additional 30 day extension.

The proposal will now head for a final Senate vote before moving to the Republican controlled House of Representatives. Trump is expected to veto the measure if it reaches his desk, and overriding a presidential veto would require a two-thirds majority in both chambers a highly difficult threshold to achieve.