A U.S. Marine Corps AH-1Z Viper helicopter conducts maritime operations in the U.S. Central Command area of responsibility on May 17, 2026. (U.S. Marine Corps)
WASHINGTON — The Senate advanced legislation Tuesday to halt the conflict with Iran as a growing number of Republicans supported Democrats in their eighth attempt to place limits on President Donald Trump’s ability to wage war.
A fourth Republican who had previously opposed such efforts, as well as the absence of several Republicans, allowed the resolution to be discharged from committee and advanced to the floor for a formal vote.
The procedural vote to move forward with the measure was 50-47, with Sen. Bill Cassidy of Louisiana breaking with his party for the first time following his loss in a primary this weekend.
Cassidy joined Republicans Susan Collins of Maine, Lisa Murkowski of Alaska and Rand Paul of Kentucky in voting with Democrats. John Fetterman of Pennsylvania again voted against the measure.
Republicans John Cornyn of Texas, Thom Tillis of North Carolina and Tommy Tuberville of Alabama did not vote.
The vote came a day after President Donald Trump said he had called off a plan to launch a new wave of attacks on Iran after three Persian Gulf nations requested additional time for “serious negotiations.”
Sen. Tim Kaine of Virginia, a Democrat who has led the effort to assert congressional powers on Iran, said the push for diplomacy presented an opportune window for lawmakers to weigh in.
“This is exactly the time where Congress should be having a debate about the rationale for the war, the status of the war, the plans to reopen the Strait of Hormuz,” he said.
Republicans have so far resisted challenging the president’s authority to use military force abroad, arguing in the case of Iran that it would put troops at risk to suddenly pull them from the conflict.
After Trump declared on May 1 that hostilities with Iran had terminated due to a ceasefire, many Republicans said resolutions to halt unauthorized action against Tehran were no longer relevant.
Democrats and some Republicans have expressed skepticism that hostilities have ended, pointing to the 50,000 troops still deployed in the region, recent exchanges of fire and the U.S. naval blockade of Iranian ports.
Navy Adm. Brad Cooper, the head of U.S. Central Command, told the House Armed Services Committee on Tuesday that the ongoing ceasefire has “set the foundation” for military hostilities to cease, but “Iran pushes it.”
He acknowledged that the state of preparedness in the region remained at the highest level and that American troops were still in harm’s way “depending on a variety of different contingencies.”
The 1973 War Powers Act allows the president to deploy American forces into hostilities without congressional authorization for up to 60 days. After that, the president must seek approval to continue the fight or ask for a 30-day extension to safely withdraw troops.
The Senate vote to advance the war powers measure on Tuesday is expected to be symbolic — similar resolutions have so far failed in the House, and they have little chance of ultimately being enacted given Trump’s veto power.
Still, Minority Leader Chuck Schumer of New York said Democrats will not let up and will continue to force votes on resolutions to stop the war in Iran and assert Congress’s constitutional war powers.
“Today proved our pressure is working: Republicans are starting to crack, and momentum is building to check him,” he said in a statement after the vote, referring to Trump.
