The US Congress on Wednesday gave its final approval to a bid to restrain President Donald Trump from attacking Iran, a sign of politicians’ alarm after soaring tension.
A month after the resolution cleared the Senate, controlled by Mr Trump's Republican Party, the Democratic-led House voted 227-186 to approve the measure that bars any military action against Iran without an explicit vote from Congress.
But the resolution is virtually certain to be vetoed by Mr Trump, and the coalition of most Democrats and some Republicans lacks the votes to override him.
"If President Trump is serious about his promise to stop endless wars, he will sign this resolution into law," said Senator Tim Kaine, the Democrat who led the move.
The House voted moments after rockets fired on a military base north of Baghdad killed an American soldier, a British soldier and a US contractor, in the deadliest such attack on foreign forces in Iraq in several years.
A similar attack in December that killed a US contractor set off a chain of escalation after the US blamed it on Iran-backed militias.
On January 3, Mr Trump ordered a drone strike that killed Iran's most powerful general, Qassem Suleimani, at the Baghdad airport.
Supporters of the resolution said they wanted to ensure that Congress had the unique power to declare war, as outlined in the US Constitution.
"There are a lot of countries in the world where one person makes the decision. They're called dictators," said Steny Hoyer, the second highest-ranking Democrat in the House.
"Our founding fathers did not want dictators running America."
Mike McCaul, the top Republican on the house foreign affairs committee, denounced the resolution and said that it should instead state that the killing of Suleimani made Americans safer.
"The enemies of our country are watching this debate right now," Mr McCaul said in a speech met with loud cheers from Republicans.
"They need to know that if you kill Americans, you will pay the price."
Six Republicans and six Democrats crossed party lines in the House.
In the Senate, eight Republicans bucked their leadership, with one complaining that a briefing by the Trump administration on Iran had been the worst he had ever heard on any military issue.
The resolution, if it becomes law, would not stop Mr Trump or future US presidents from taking military action if they determine there is an imminent threat from Iran.
The Suleimani strike angered Iraqi leaders, who called for the US forces to be removed from the country.
Some questioned whether militias carried out the attack in a country that still is trying to eliminate ISIS.
Mr Trump, who has vowed to pull out troops around the world and recently sealed a deal with Afghanistan's Taliban, responded furiously to Iraqi threats to eject US forces, threatening to impose sanctions.
About 5,200 US troops are in Iraq as part of an international coalition formed in 2014 to confront ISIS.
