The 214-213 vote, with one abstention, was held after Democrats forced the issue onto the floor. It came as unease over the six-week conflict continued to spread on Capitol Hill, with lawmakers wary of rising costs, an unclear endgame and the risk of a wider war.

The measure would have required Trump to end US military operations against Tehran unless Congress explicitly approved them, invoking the 1973 War Powers Resolution that limits presidential freedom to conduct prolonged hostilities without lawmakers' consent.