The House of Representatives approved Friday an amendment to the annual defense spending bill to curtail military action by President Donald Trump to attack Iran.
The bipartisan measure was approved 251-170 with nearly 30 Republicans joining nearly all Democrats in support.
The amendment prohibits Trump from attacking Iran without prior congressional approval, but would not bar the president from striking in retaliation for an Iranian attack.
“This is the most effective way to ensure Trump follows our constitution and doesn’t drag us into another costly war in the Middle East," congressman Ro Khanna, the provision's author, said on Twitter.
"Constitutional rights aren’t optional and endless war isn’t inevitable," he added.
Trump last month came close to launching strikes on Iranian targets following Tehran's downing of an American reconnaissance drone that Iran says breached its airspace. The averted strikes, Trump said, would have resulted in dozens of Iranian casualties.
They also had the possibility of spawning a much wider conflict with Iran and its allies that could have spanned the region.
Trump has continued his series of bellicose threats to Iran, warning the Islamic Republic in one instance of "obliteration" if it attacks additional American targets.
The president has insisted he has the authority to strike Iran without prior congressional approval despite the Constitution's delegations of war powers solely to Congress.
Friday's vote signifies growing war weariness amongst members Congress and the wider American public, as well as efforts by some lawmakers to reclaim their Constitutional war powers after nearly two decades of broad leeway given to successive presidents.