US President Donald Trump on Monday warned that any Iranian “fast-attack” ships approaching the US-imposed maritime blockade on Iran would be “eliminated”.

The warning came shortly after the United States enforced a blockade targeting ships entering and departing Iranian ports. 

In a post on Truth Social, Trump claimed that Iran’s navy had been “completely obliterated” during the six-week conflict between the two countries, but noted that a small number of “fast-attack ships” had not been targeted. “What we have not hit are their small number of, what they call, ‘fast attack ships,’ because we did not consider them much of a threat,” he said.

“Warning: If any of these ships come anywhere close to our BLOCKADE, they will be immediately ELIMINATED, using the same system of kill that we use against the drug dealers on boats at Sea. It is quick and brutal,” Trump wrote.

Trump was referring to the dozens of US strikes carried out against suspected drug boats in the Caribbean and Pacific since September in a campaign that has killed at least 110 people. Iran has effectively closed the Strait of Hormuz, cutting off a vital waterway that normally carries about a fifth of global oil and liquefied natural gas supplies, in retaliation for US-Israeli strikes.

Iran's conventional navy has largely been destroyed, but Iran's Islamic Revolutionary Guard Corps still have plenty of options, including fast-attack craft, mini submarines, mines and even jet skis packed with explosives, said Tom Sharpe, a retired Royal Navy commander, last month.