WASHINGTON (AP) — The House is expected to vote on legislation Thursday to compel President Donald Trump to withdraw from the war with Iran, a significant test of lawmakers' willingness to go along with a conflict the president launched over two months ago without congressional approval.

Watch the House floor live in the video player above.

The vote is the latest effort by Democrats to rein in Trump's military campaigns by using the War Powers Resolution of 1973. Previous votes on similar resolutions have failed, but Democrats are hoping that Thursday could be a turning point.

One by one, a small but potentially crucial number of Republicans have sided with Democrats to check Trump's power to continue the conflict. On Tuesday, the Senate advanced another war powers resolution on the Iran war when four GOP senators supported the resolution and three others were absent from the vote.

A final vote on the Senate resolution could also come Thursday, though Republican leaders expect they'll be able to block it once every GOP senator is present.

Frustration with Iran war grows on Capitol Hill

On Capitol Hill, patience with the war has grown thin as the stalemate in the Strait of Hormuz disrupts global shipping and elevates gas prices in the U.S. Another House war powers resolution nearly passed last week, falling on a tie vote as three Republicans voted in favor.

Democratic Rep. Gregory Meeks of New York, who sponsored the war powers resolution, has said he expects to have the votes this time around.

"Congress has a constitutional duty. It has a duty to act, not to cheerlead, especially not to cheerlead an open-ended war of choice," Meeks said.

The lone Democrat who voted against the war powers resolution last week, Rep. Jared Golden of Maine, has said he will vote in favor of the legislation this time. Meanwhile, leaders of both parties have been dealing with several absences that could shift the vote either way in the closely divided chamber.

Republicans have been broadly supportive of Trump's efforts to destroy Iran's nuclear capabilities, but some are now saying that the president's legal timeline to wage a war without congressional approval has expired. Under the War Powers Resolution of 1973, presidents have 60 days to engage in a military conflict before Congress must either declare war or authorize the use of military force.

"We have to follow the law," said Rep. Brian Fitzpatrick, a Pennsylvania Republican shortly after he voted for an Iran war powers resolution for the first time last week.

The dispute over war powers

The White House argues that the requirements of the War Powers Resolution no longer apply because of the ceasefire with Iran. At the same time, Trump has said he was just an hour away from ordering another strike on Iran earlier this week, but held off because Gulf allies said they were engaged in negotiations to end the war.

Still, Trump said on social media that military leaders should "be prepared to go forward with a full, large scale assault of Iran, on a moment's notice, in the event that an acceptable Deal is not reached." Trump has repeatedly set deadlines for Tehran and then backed off.

Sen. Thom Tillis, a Republican who has so far voted against the war powers resolutions, expressed frustration with the Trump administration's stance, especially from Defense Secretary Pete Hegseth.

"The current status quo, Pete Hegseth demonstrates how incompetent he is," Tillis told reporters, adding that he would be willing to vote for an authorization for use of military force.

Meanwhile, Democratic senators rallied outside the Capitol Wednesday alongside VoteVets, a left-leaning veterans' advocacy group. They placed signs on the Capitol lawn noting that the nationwide average price of gasoline had risen to $4.53.

Sen. Tammy Duckworth, an Illinois Democrat who served in the Iraq War with the Air National Guard, argued that the Iran war has amounted to a strategic blunder for Trump.

"Trump started a war, and he's made things worse than before," Duckworth said, pointing to Iran's new leadership and the country's willingness to put a chokehold on commercial shipping through the Strait of Hormuz.

Republican leaders praised Trump for taking what they said was bold action to directly confront Iran, a nation that has been a U.S. adversary for decades.

"I'm an American. I don't believe in getting hit and walking away and pretending as though it didn't happen," said Rep. Brian Mast, the Republican chair of the House Foreign Affairs Committee.

For Congress, the growing momentum to pass a war powers resolution could eventually lead to a legal showdown over who has the final authority over military conflicts.

The legislation before the House Thursday is a concurrent resolution that lawmakers say would take effect without Trump's signature if it passes both chambers of Congress.

But Trump has also argued that the 1973 law — passed by Congress during the Vietnam War era in an attempt to take back its power over foreign conflicts — is unconstitutional.

Associated Press writer Joey Cappelletti contributed to this report.