The U.S. House of Representatives on Wednesday voted to restrict U.S. President Donald Trump's authority to continue military operations against Iran, with four Republicans joining Democrats.

The resolution, which passed by a 215-208 vote, directed Trump to withdraw U.S. forces from the war against Iran unless Congress authorizes further military action.

The vote came after three previous war powers resolutions failed in the House by slim margins. In the Senate, seven similar attempts have also failed.

Even if the measure passes both chambers, it would almost certainly be vetoed by Trump.

Trump was overwhelmingly backed by his fellow Republicans when the war started. However, as the war dragged on with no clear end in sight, some Republicans began to waver.

With the midterm elections approaching and gasoline prices continuing to rise, Republicans are increasingly concerned that the war would hurt the GOP's prospects in the November elections.