The Senate advanced legislation Tuesday that would direct President Donald Trump to withdraw American forces from the Iran conflict unless Congress formally authorizes continued military operations or declares war.
Lawmakers approved the resolution in a 50-47 vote, clearing a key procedural hurdle for the measure. The resolution is based on the 1973 War Powers Resolution, which limits how long a president can keep U.S. troops involved in hostilities without congressional approval.
The vote gained major attention after Sen. Bill Cassidy of Louisiana joined Democrats and three other Republicans in supporting the measure. Cassidy had previously voted against similar efforts earlier this year, but his reversal helped provide the decisive margin.
The other Republicans who backed the resolution were Sen. Rand Paul of Kentucky, Sen. Susan Collins of Maine and Sen. Lisa Murkowski of Alaska. Sen. John Fetterman of Pennsylvania was the only Democrat to vote against it.
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Three Republican senators, John Cornyn of Texas, Thom Tillis of North Carolina and Tommy Tuberville of Alabama, were absent from the vote.
Senate Minority Leader Chuck Schumer praised the result and said the vote showed growing momentum to check Trump’s war powers.
Republicans are starting to crack, and momentum is building, Schumer said after the vote. He added that Democrats would continue pushing the issue.
Cassidy explained his change in position before the vote, saying he still supports efforts to stop Iran’s nuclear program but believes Congress has not received enough information from the White House and Pentagon about Operation Epic Fury.
While I support the administration’s efforts to dismantle Iran’s nuclear program, the White House and Pentagon have left Congress in the dark, Cassidy wrote on X.
He said that without more clarity from the administration, Congress should not authorize or extend U.S. involvement.
Cassidy’s vote came shortly after he lost his Republican primary in Louisiana. Trump had endorsed Cassidy’s challenger, Rep. Julia Letlow, who advanced after receiving the largest share of the vote. Louisiana Treasurer John Fleming also moved forward, while Cassidy finished behind both candidates.
The vote reflects growing pressure in Congress as the Iran conflict continues raising questions over presidential authority, military strategy and the economic cost of prolonged operations.
Sen. Mike Rounds of South Dakota, who has supported the initial strikes on Iran’s nuclear sites, said the War Powers Resolution gives lawmakers a path to debate the issue.
Some senators believe it is time for Congress to have that debate, Rounds said.
Democrats have also pointed to rising prices as a reason for urgency. Sen. Chris Murphy of Connecticut said Americans are feeling the consequences of the conflict through higher grocery and gas prices while peace negotiations remain stalled.
The resolution would require Trump to pull U.S. troops from the conflict unless Congress acts. The administration has argued that a fragile ceasefire after the initial strikes ended active hostilities, potentially affecting whether the War Powers Resolution applies.
The Iran conflict began after U.S. and Israeli forces launched strikes against Iranian targets at the end of February. The U.S. operation, known as Operation Epic Fury, targeted Iranian nuclear sites and senior regime figures.
Trump formally notified Congress on March 2 that U.S. forces had entered combat operations, triggering the 60-day timeline under the War Powers Resolution.
Previous attempts to limit or end U.S. involvement in Iran had failed in the Senate, with Republicans blocking similar resolutions. Tuesday’s vote showed that support for congressional oversight has grown, especially as concerns rise over military costs, energy prices and the risk of a longer conflict.
Even if the resolution continues moving forward, it still faces major obstacles. If it reaches Trump’s desk, supporters would likely need a veto-proof majority to force it into effect over the president’s opposition.
For now, the vote marks a significant political setback for the administration and a clear sign that some Republicans are willing to challenge Trump’s handling of the Iran conflict.
The Republican-led US Senate signaled opposition to continuing the Iran war in a procedural vote, reflecting deepening political unease over a foreign conflict that is taking a mounting financial toll on Americans https://t.co/lCuKrFk6Mk
— Bloomberg (@business) May 19, 2026
