U S. President Donald Trump doubled down Monday on his threat to wreck Iran's civilian infrastructure, warning U.S. forces could destroy every bridge and power plant in the country within four hours and that a truce proposal from international mediators was not yet enough.

Five weeks into the Middle East war triggered by a joint U.S.-Israeli air assault on Tehran, the U.S. leader has demanded that Iran reopen the Strait of Hormuz to international shipping by midnight GMT on Tuesday, or face a newly devastating round of bombing.