Democrat announces major showdown with Trump

Schumer threatened that Democrats would use the "power of the purse" to cut off funding to the Department of Defense if necessary to bring the conflict to a swift end.

"We will end the war. We already have some Republicans joining us in bringing the war to an end, and the Founding Fathers established the power of the purse as one of the ways to restrain a president who wages war without the consent of the American people," Schumer said at a press conference at the headquarters of the Democratic Senatorial Campaign Committee (DSCC) in Washington on Wednesday.

Four Republican senators joined Democrats in supporting a war powers resolution directing President Trump to withdraw US troops from hostilities against Iran unless Congress formally authorizes the use of military force.

Republican Senators Tom Tillis, Susan Collins, Lisa Murkowski and Rand Paul voted to advance the Iran war powers resolution when it was last brought before the Senate.

Senator Bill Cassidy (Republican from Louisiana) was undecided about how to vote but ultimately voted against the measure in late September after meeting with Senate Republican leaders in the Mansfield Room, outside the Senate chamber.

Cassidy voted in favour of the Iran war powers resolution in June but later changed his vote after a heated confrontation with Trump during a private meeting.

However, even if the Senate passes a war powers resolution with the force of law, Trump could still veto it, and Democrats do not have enough votes to override his veto.

Democrats have greater leverage over Trump's handling of the war through blocking Pentagon funding.

In June, the White House requested nearly $70 billion in emergency funding for the Pentagon, but the request stalled amid strong Democratic opposition.

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The annual defence appropriations bill is also stalled.

Democrats are threatening to block the annual National Defense Authorization Act (NDAA) and the defence spending bill as long as the country remains at war with Iran.

"My personal view is that if the war ends, there is an opportunity for bipartisan cooperation on defence authorization and defence appropriations. I think that if the war does not end, it will be extremely difficult," Senator Brian Schatz (Democrat from Hawaii), who is next in line to become Senate Democratic leader, told reporters several weeks ago.