US Senate to vote on Trump's war powers as Iran conflict continues

The US Senate is set to vote on a war power resolution aimed at limiting President Donald Trump's ability to order further military action in Iran.

The measure would require the withdrawal of US forces from the conflict unless Congress approves the operation. But previous efforts have failed, and it is unclear how much its success would change the war.

Democrats argue that Trump sidelined Congress and has offered shifting reasons for the war. Most Republicans say they will block the resolution, but may change their stance if the war expands.

The vote comes five days after the US and Israel began striking Iran. Iran has responded by launching attacks on Israel and US-allied states in the Gulf.

Since then, some lawmakers have been on edge, waiting to see what role, if any, they will play in the ongoing attacks.

"Every senator will have to go on the record to declare whether it is in our best interest to send our sons and daughters into conflict against Iran," said Senator Tim Kaine, a Virginia Democrat who sponsored the legislation.

"I pray that my colleagues will vote to end this dangerous and unnecessary war that has already resulted in the loss of six service members and injured others."

A majority of Democrats in the Senate are expected to back the measure. The exact number of Republicans who will support it remains unclear, but the bill would need a majority - more than 50 votes - to pass.

If it passes, it would still need to go through the US House of Representatives, which is expected to vote on Thursday.

It would then need survive an expected veto from the president. To override a veto, both chambers would have to pass the measure with a two-thirds majority.

While the president has broad authority to launch military action without a formal declaration of war, Congress, by law, must be notified within 48 hours of hostilities beginning.

Secretary of State Marco Rubio has repeatedly said that the Trump administration has complied with that requirement.

Top congressional leaders were notified before the initial strikes began, and Trump informed Congress in a letter on Monday - though he maintained it was not necessary.

Trump has previously ordered military operations without congressional approval, such as the US strikes against Iranian nuclear facilities last year, and the seizing of Venezuela's President Nicolás Maduro in January.

"To begin with, no presidential administration has ever accepted the War Powers Act as constitutional – not Republican presidents, not Democratic presidents," Rubio, a former senator, said.

Congress passed the War Powers Resolution, or Act, in 1973 to constrain the ability of then-President Richard Nixon to wage war in Vietnam. It requires the 48-hour notification and passage by Congress within 60 days of an Authorization to Use Military Force (AUMF) or official declaration of war.

Since 2001, administrations have relied on the AUMF passed after the 9/11 attacks as justification for the use of military force in the Middle East. Multiple attempts to repeal that authorisation have been unsuccessful.