U.S. Senate Republicans backed President Donald Trump's military campaign against Iran on Wednesday, voting to block a bipartisan resolution aiming to stop the air war and require that any hostilities against Iran be authorized by Congress.

As voting continued, the tally in the 100-member Senate was 52 to 47 not to advance the resolution, largely along party lines, with almost every Republican voting against the procedural motion and almost every Democrat supporting it.

The latest effort by Democrats and a few Republicans to rein in President Donald Trump's repeated foreign troop deployments, sponsors described the war powers resolution as a bid to take back Congress' responsibility to declare war, as spelled out in the U.S. Constitution.

Opponents rejected this, insisting that Trump's action was legal and within his right as commander in chief to protect the United States by ordering limited strikes.

"This is not a forever war, indeed not even close to it. This is going to end very quickly," Republican Senator Jim Risch of Idaho, chairman of the Senate Foreign Relations Committee, said in a speech against the resolution.

The measure had not been expected to succeed. Trump's fellow Republicans hold slim majorities in both the Senate and House of Representatives, and have blocked previous resolutions seeking to curb his war powers.