The measure, which would mark a rare wartime rebuke to a sitting commander-in-chief, survived a key procedural vote -- the first time either chamber of Congress had advanced legislation seeking to limit Trump's military operations against Tehran since the war began more than 11 weeks ago.

But it still has to pass a final vote and, even then, would face major obstacles in the Republican-controlled House of Representatives, which has already rejected similar efforts.

And it would almost certainly be vetoed by Trump if it reached his desk.

The vote nevertheless underscored growing unease inside the president's party as the conflict stretches into its third month, straining US weapons stockpiles, raising questions over military readiness and driving official cost estimates above $30 billion to date.

The resolution would require the administration to halt military action against Iran unless Congress explicitly authorizes the conflict, invoking the 1973 War Powers Act passed after the Vietnam War to restrain prolonged military campaigns launched without lawmakers' approval.

"This president is like a toddler playing with a loaded gun," Democratic Senate Minority Leader Chuck Schumer said ahead of the vote.

"If there was ever a time to support our war powers resolution to withdraw troops from hostilities with Iran, it's now."