President Trump said the U.S. Navy will start guiding ships from foreign countries through the Strait of Hormuz from Monday and warned that if Iran tries to disrupt the process the American military will use force. Why it matters: This move that Trump called "Project Freedom" is the most significant step by his administration to try and reopen the key strait since Iran shut it down early in the war. While Trump claims the move is "humanitarian," it is a clear U.S. challenge to Tehran's effort to control the strait. An Iranian military response could spark a confrontation or even an escalation back to war. What he's saying: Trump wrote on Truth Social that countries from around that are not involved in the war but have ships that are stuck in the strait have asked the U.S. to help free them. Many of these ships are running low on food, and other supplies for their crews and suffer from health and sanitary problems, Trump said.'The Ships movement is merely meant to free up people, companies, and Countries that have done absolutely nothing wrong — They are victims of circumstance. This is a Humanitarian gesture on behalf of the United States, Middle Eastern Countries but, in particular, the Country of Iran," Trump said. "We have told these Countries that we will guide their Ships safely out of these restricted Waterways, so that they can freely and ably get on with their business," he added. "If, in any way, this Humanitarian process is interfered with, that interference will, unfortunately, have to be dealt with forcefully."The intrigue: It was not immediately clear whether this move was coordinated with Iran in any way. Iranian officials did not immediately respond publicly to Trump's announcement.The big picture: Trump wrote his representatives "are having very positive discussions" with Iran and stressed these discussions "could lead to something very positive for all." The U.S. sent on Sunday another amended draft for an agreement to end the war in response to Iranian officials' latest proposal, sources said. Editor's note: This article has been updated with more context.