The US Senate backed legislation on Thursday to limit President Donald Trump’s ability to wage war against Iran, rebuking him weeks after a strike against an Iranian military commander and Tehran’s retaliation 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 US 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 to muster the two-thirds Senate super majority to override. Fifty-three of the 100 senators are Republicans who rarely break with the President.

Senators voted nearly along party lines a week ago to acquit Trump of impeachment charges, after an investigation and trial that underscored Washington’s bitter partisan divides.

Opponents said the resolution’s passage sent the wrong message.

“We need to send a message of firmness, and not weakness,” said Senator Jim Risch, the Republican chairman of the Senate Foreign Relations Committee.