The U.S. Congress could vote as soon as next week on whether to block President Donald Trump’s ability to strike Iran without lawmakers’ approval, as the U.S. military prepares for a potential serious conflict with Iran if diplomatic efforts fail.

Members of Congress, including a few of Trump’s fellow Republicans as well as Democrats, have tried – and failed – repeatedly to pass resolutions that would bar Trump from military action against foreign governments without lawmakers’ approval.

The U.S. Constitution grants Congress, not the president, the power to send U.S. troops to war, except for limited strikes for national security reasons. Reuters reported last week that the military is preparing for the possibility of sustained, weeks-long operations if Trump orders an attack.

Trump’s Republicans hold slim majorities in both the Senate and House and have blocked the resolutions, arguing that Congress should not restrict Trump’s national security powers.

Democratic Senator Tim Kaine of Virginia and Republican Senator Rand Paul of Kentucky filed a Senate resolution late last month to block hostilities against Iran unless explicitly authorized by a congressional declaration of war.

“If some of my colleagues support war, then they should have the guts to vote for the war, and to be held accountable by their constituents, rather than hiding under their desks,” Kaine said in a statement on Friday, as U.S. military assets moved toward Iran.

An aide to Kaine said on Friday there was no timetable yet as to when the Senate might take up the resolution.

In the House of Representatives, Republican Thomas Massie of Kentucky and Democrat Ro Khanna of California said they planned to force a vote on a similar resolution next week.

“Trump officials say there’s a 90% chance of strikes on Iran. He can’t without Congress,” Khanna said in a post on X.com.

—

(Reporting by Patricia Zengerle; editing by Diane Craft)