Donald Trump has issued a “shoot to kill” order for Iranian boats laying mines in the Strait of Hormuz.
The president said he has also directed the US navy to step-up clearance of the explosive devices from the critical Gulf waterway.
Meanwhile, the American military seized another tanker suspected of smuggling Iranian oil in the Indian Ocean.
The seizure comes after Iran attacked three cargo ships on Wednesday in the strait, capturing two of them.
On Tuesday, Mr Trump extended a ceasefire while maintaining an American blockade of Iranian ports.
The conflict and ensuing stand-off between the US and Iran has effectively closed the critical shipping route, sending energy prices soaring and damaging the global economy.
Mr Trump wrote on his Truth Social platform: “I have ordered the United States Navy to shoot and kill any boat, small boats though they may be (Their naval ships are ALL, 159 of them, at the bottom of the sea!), that is putting mines in the waters of the Strait of Hormuz. There is to be no hesitation.
“Additionally, our mine ‘sweepers’ are clearing the Strait right now. I am hereby ordering that activity to continue, but at a tripled up level! Thank you for your attention to this matter. President DONALD J. TRUMP.”
In a further post a short time later, he added: “Iran is having a very hard time figuring out who their leader is! They just don’t know!
“The infighting is between the ‘Hardliners’, who have been losing BADLY on the battlefield, and the ‘Moderates’, who are not very moderate at all (but gaining respect!), is CRAZY!
“We have total control over the Strait of Hormuz. No ship can enter or leave without the approval of the United States Navy. It is ‘Sealed up Tight’, until such time as Iran is able to make a DEAL!!! Thank you for your attention to this matter. President DONALD J. TRUMP.”
The impasse has plunged into doubt the prospect of further talks aimed at securing a lasting end to hostilities.
Tehran has insisted the US blockade must be lifted.
The speaker of Iran’s parliament and the country’s chief negotiator Mohammad Baqer Qalibaf said: “You did not achieve your goals through military aggression and you will not achieve them by bullying either.
“The only way is recognising the Iranian people’s rights.”
In a show of defiance this week, large crowds turned out for a parade in Tehran, where the regime put on show some of its ballistic missiles, while banners proclaimed the strait was “Indefinitely under Iran’s Control” and “Trump could not do a damn thing”.
Meanwhile, military planners from a coalition of countries have continued to meet in London as part of plans for a UK and France-led defensive mission to keep the vital maritime passage open once the Iran war is over.
Defence Secretary John Healey and his French counterpart Catherine Vautrin said in a joint message to them: “This multinational military planning conference matters.
“Your task is to translate the diplomatic consensus set by our leaders into practical military options, with a co-ordinated joint plan to safeguard freedom of navigation in the strait and support a lasting ceasefire.
“Turning diplomatic momentum into action demands sharp planning, frank discussion and firm commitments from allied and partner nations, and we are grateful to those nations who have already indicated their willingness to contribute.
“We are confident that real progress can be made.”
