DONALD Trump has threatened to "blow off Iran from the face of earth" if they attack US vessels in the Strait of Hormuz.

The US President told Fox News about its plans after he deployed 15,000 troops to escort stranded vessels through the key shipping route as part of "Project Freedom."

He described blockade as "the largest military exercise in history," adding: "We have more weapons and ammunition and we are at a much higher level than before."

Iran has repeatedly threatened to attack US forces in the key waterway – where an estimated 2,000 ships are currently stuck.

Donald Trump announced the start of "Project Freedom" on Monday to free ships – deploying 15,000 troops and 100 aircraft for the operation.

The US military said Navy guided-missile destroyers are "helping to restore transit for commercial shipping".

US Central Command said: "As a first step, 2 U.S.-flagged merchant vessels have successfully transited through the Strait of Hormuz and are safely headed on their journey."

Tehran threatened to attack any ships "interfering" in the trade passage in response to Trump's move.

It later said a US warship was hit with two missiles and was forced to turn back after repeating warnings not to cross.

The Iranian army said: "With a firm and swift warning from the Islamic Republic Navy, the entry of American and Zionist enemy destroyers into the Strait of Hormuz was prevented."

US Central Command rejected reports that a warship was hit near Jask, a port on Iran's southern coast, citing local sources.

Iran has also denied US claims that two vessels had travelled through the strait – calling them "outright lies".

A suspected strike also hit a South Korean vessel anchored in the Starit of Hormuz, Seoul said.

It comes after an earlier reported strike on a separate tanker linked to Adnoc, the UAE's state oil firm.

Trump previously warned Iran they would be "dealt with forcefully" if anyone tried to sabotage his plans.

He dubbed the operation "Project Freedom".