The Senate backed legislation Thursday to limit President Donald Trump’s ability to wage war against Iran, rebuking him after a strike against an Iranian military commander and Tehran’s retaliation last month raised fears of broader regional conflict.

Eight of Trump’s fellow Republicans joined Democrats to pass the war powers resolution by 55-45. The measure would require Trump to remove U.S. troops engaged in hostilities against Iran unless Congress declares war or passes a specific authorization for the use of military force.

Trump has promised a veto and there is not expected to be enough support in the Senate to muster the two-thirds majority to override. Republicans in the chamber hold 53 of the 100 seats and rarely vote against the president.