The White House on Monday endorsed the US Congress’s efforts to repeal the nearly two decade-old military authorisation that allowed former president George W Bush to invade Iraq in 2003.
President Joe Biden's intent to sign the repeal legislation – introduced by Democrat Barbara Lee of California – significantly increases the odds of taking the 2002 authorisation off the books.
A repeal would ensure a president will no longer be able to use the authorisation as a legal basis for military action in Iraq.
Mr Biden's team backed the legislation, saying "the United States has no ongoing military activities that rely solely on the 2002 [authorisation] as a domestic legal basis and repeal of the 2002 [authorisation] would likely have minimal impact on current military operations".
Under US law, Congress must authorise military action abroad except in cases of imminent self-defence – though presidents of both parties have frequently launched offensive military action in countries such as Libya and Syria without congressional authorisation.
The House of Representatives is expected to vote on the repeal later this week, where it is expected to pass, largely along party lines.
Most Republicans argue that Congress has not consulted enough with the relevant US agencies and the Iraqi government, and are wary of a stand-alone repeal without a replacement.
About 2,500 US troops remain in Iraq on an official mission to fight the remnants of ISIS. However, they are stationed in the country under a separate 2001 military authorisation that Congress passed after the 9/11 attacks.
Nonetheless, American troops in Iraq have increasingly found themselves in the crosshairs of the regional rivalry between Washington and Tehran, with Iran-backed militias in Iraq frequently firing on US soldiers stationed throughout the country.
The frequent exchange of fire between the pro-Iran militias and US forces last year prompted former president Donald Trump to order a strike that killed Iranian commander Qassem Suleimani and Iraqi Popular Mobilisation Forces commander Abu Mahdi Al Muhandis in Baghdad.
The Trump administration invoked the 2002 Iraq war authorisation as part of its legal justification for the Suleimani strike, which prompted Iran to retaliate with a barrage of missile attacks on the Ain Al Asad base in Iraq, causing traumatic brain injuries to more than 100 US soldiers.
Several Trump administration officials also implied that the 2002 Iraq war authorisation could allow the president to take military action against Iran because of Tehran’s support for Iraqi Shiite militias.
Mr Biden responded to a more recent increase in attacks on US forces in February by striking two Iran-backed Iraqi militias stationed in Syria.
The Biden administration did not invoke the 2002 Iraq war authorisation to justify the Syria strike and instead argued it was legal under Article II of the constitution, which gives the president the right to use military force to defend US troops.
However, the Biden administration has not provided any public evidence that the Syria strike thwarted an imminent attack on American forces, prompting some pushback from within his own party.
Ms Lee and several other Democrats are also pushing to repeal the 2001 military authorisation, which several presidents have used as the legal basis for military operations in more than 40 countries against terrorist groups such as Al Qaeda and ISIS.
Repealing the 2001 authorisation would raise legal questions about the Biden administration’s ability to maintain a troop presence in Iraq and the White House has indicated that it would not support a full repeal of that law without a replacement.
“The president is committed to working with the Congress to ensure that outdated authorisations for the use of military force are replaced with a narrow and specific framework appropriate to ensure that we can continue to protect Americans from terrorist threats,” the White House said.
“As the administration works with the Congress to reform [military authorisations], it will be critical to maintain the clear authority to address threats to the United States’ national interests with appropriately decisive and effective military action.”