Washington, DC - The United States House of Representatives on Thursday approved a nonbinding resolution aimed at reining in the president's ability to attack Iran in the future without congressional approval.

The resolution comes as criticism over US President Donald Trump's decision to order the killing of Iranian military leader Qassem Soleimani in Iraq intensifies. Congress was not consulted prior to the assassination, angering Democrats who fear Trump's actions could trigger a cycle of escalation leading to war.

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The House's War Powers resolution directs Trump to terminate military operations against Iran except for self-defence and clarifies that the president presently does not have congressional authority to engage in war with Iran. A similar version is expected to be debated in the Senate.

Thursday's House vote 224-194 fell along party lines and followed days of frustration by Democrats over Trump actions regarding Iran. Three Republicans and one Independent sided with the Democrats. Eight Democrats voted with Republicans against the resolution.

Congress was not consulted prior to the assassination of Soleimani, angering many Democrats who fear Trump's actions could trigger a cycle of escalation leading to war.

Trump's decision to order the drone attack on Soleimani was "provocative and disproportionate", Democratic House Speaker Nancy Pelosi said.

The lead sponsor of the House resolution was Democrat Elissa Slotkin, a former CIA analyst who served three tours in Iraq and specialised in tracking Iranian-backed Shia militia groups.

"I have followed Iran's destabilising activity in Iraq up close for my entire professional career," Slotkin said during floor debate.

"I have watched friends and colleagues hurt or killed by Iranian rockets, mortars and explosive devices," she added. "If our loved ones are going to be sent to fight in any protracted war, the president owes the American public a conversation."

Under the US Constitution, the authority to direct military action is divided between Congress and the president. Congress has the power to declare war while the president, as commander-in-chief, has the power to use the military to defend the US.

The War Powers Act of 1973 provides that Congress may direct the president to withdraw US forces from hostilities by passing a resolution in both the House and Senate.

Iran responded to Soleimani's assassination with missile attacks against Iraqi bases housing US troops. Trump said on Wednesday there were no US or Iraqi casualties. He welcomed an apparent pause in hostilities, but announced new economic sanctions on Iran.

US Speaker of the House Nancy Pelosi answers questions during a news conference at the US Capitol [Win McNamee/Getty Images/AFP]

Justifying Soleimani's killing, the Trump administration said the leader of Iran's elite Quds Force was planning an "imminent" attack on US forces in Iraq.

"In targeting Soleimani, this president took bold and decisive action that was long overdue and he ought to be supported," said Representative Steve Chabot, a Republican.

Republicans attacked Democrats during the debate for showing a lack of patriotism in failing to support the Trump for killing Soleimani who is believed to have orchestrated attacks that killed or wounded an estimated 600 US troops during the wars in Iraq and Afghanistan.

"I know most in here haven't seen or smelled or touched that kind of death, but let me tell you about it," said Representative Brian Mast, who lost both legs as a Special Forces bomb disposal expert in Afghanistan.

"They were burned alive inside of the Humvees. Their lungs were scorched by the flames of the explosions. Vehicle fragments were blown into their skulls," said Mast, who walks with prosthetic legs and was elected to Congress in 2016.

Democrats countered that it is for those same risks to some 60,000 US troops now deployed in the Middle East and North Africa, Congress must provide a check on Trump's actions to prevent an escalation with Iran.

"If we are going to put our troops in harm's way, we had better have a strategy. Unfortunately, we don't have a strategy," said Representative Ted Lieu, a Democrat and former Air Force officer.

"Soleimani was a malign actor who masterminded the killing of US soldiers but assassinating him has unleashed the dogs of war," Democratic Representative Gerry Connolly said in floor remarks.

"We must be prepared for further Iranian retaliation," Connolly said. "Congress must reassert its solemn constitutional duty to decide when and where the United States goes to war."

Uphill battle in Senate

In a parliamentary twist to be worked out with Senate, the War Powers resolution passed by the House would not require the president's signature. The Senate is poised to debate a similar but slightly different measure that would need the president's signature to take effect.

Two Senate Republicans, Rand Paul and Mike Lee, have signalled they will join Democrats in rebuking the president on Iran. Paul and Lee railed against Trump and his team after administration officials gave a limited briefing to senators on Wednesday.

It was "probably the worst briefing I've seen on a military issue in the nine years I've been in the United States Senate," Lee told reporters.

Senators Mike Lee and Rand Paul depart via the Senate Subway following a classified national security briefing of the US Senate on developments with Iran [Tom Brenner/Reuters]

But the effect of the congressional votes on any War Powers resolution will be largely symbolic and political, said Lawrence Korb, a national security analyst at the Center for American Progress in Washington, DC. So long as Trump retains the support of most of the 53 Republicans in the Senate, Trump can veto the measure without risk overridden.

Without "a whole defection of Republicans" in support of limiting the president's war powers, decisions to escalate against Iran will rest with the president and his advisers, Korb told Al Jazeera.

This is the second time in Trump's presidency Congress has voted against deepening US military engagement in the Middle East.

Last year, Congress rebuked Trump's authorisation of US military support for Saudi-UAE campaign in Yemen, including aerial refuelling of combat aircraft and supplies of precision munitions that were used to kill civilians.

In April 2019, the House approved a War Powers resolution on a 247-175 vote that would have blocked US military engagement in Yemen. The Senate voted 54-46 to approve the measure.

It was the first time in 47 years that Congress had invoked its constitutional authority to try to stop US involvement in a foreign conflict.

Trump vetoed the Yemen bill and Congress did not rally two-thirds majorities needed to override the president.