The United States Senate on Wednesday voted 52–47 to reject a Democratic-led resolution that would have required President Donald Trump to withdraw American forces from the conflict with Iran unless Congress formally authorised the war — the fourth such vote this year, each failing mostly along party lines. One Republican, Senator Rand Paul of Kentucky, crossed the aisle to support the measure, while one Democrat, Senator John Fetterman of Pennsylvania, voted against it.

The vote came more than six weeks after the United States and Israel launched air strikes on Iran on 28 February, and just days after a fragile two-week ceasefire was agreed. Subsequent peace talks held in Islamabad, Pakistan, broke down without a lasting agreement, though both sides have indicated openness to a second round. The conflict has already claimed more than a dozen American lives, and the US Navy is maintaining a naval blockade in the Strait of Hormuz, with Central Command reporting that no vessels had successfully crossed it in the 48 hours before the vote. Treasury Secretary Scott Bessent has signalled that Washington is preparing additional economic measures it describes as the "financial equivalent" of military strikes.

Democrats argue that Trump acted outside constitutional authority by launching the war unilaterally alongside Israel, noting that the US Constitution reserves the power to declare war for Congress. Senator Tammy Duckworth of Illinois, an Iraq War veteran, urged colleagues to fulfil what she called "the absolute minimum required of us." Senator Chris Murphy criticised the conflict as a "bungled, mismanaged war" and condemned the absence of Republican-led oversight. Republicans backing the president, however, have maintained that Trump is acting within his executive authority and within his duty to defend the country, with Senator Jim Risch dismissing the resolution as an instruction for Trump to "put his tail between his legs and run."

Nevertheless, cracks are beginning to show within Republican unity. The War Powers Act of 1973 requires Congress to authorise military action — or approve a 30-day extension — within 60 days of its start, a deadline that falls at the end of April. Several Republican senators, including Lisa Murkowski of Alaska, Susan Collins of Maine, and Thom Tillis of North Carolina, have called on the administration to present a clear strategy and seek formal authorisation. "If this conflict exceeds the 60 days specified in the War Powers Act, or if the President deploys troops on the ground, I believe that Congress should have to authorise those actions," Collins said. Senate Majority Leader John Thune, while expressing confidence in military progress, acknowledged the need for "a plan for how to wind this down."

Even if a resolution passed both chambers — which appears unlikely given the numbers required — Trump could veto it, and a two-thirds majority in each chamber would be needed to override him. Still, the approaching 60-day deadline is shaping up as the most significant constitutional test yet of this conflict's legitimacy, with the outcome of a potential second round of US–Iran talks in Islamabad likely to influence how much patience Republican lawmakers are willing to extend.