In a post on Truth Social, Trump said Washington would take action against vessels that had paid tolls to Iran and would begin clearing mines he said Tehran had deployed in the strategic waterway, a chokepoint for about 20 percent of global energy supplies.
"Effective immediately, the United States Navy … will begin the process of blockading any and all ships trying to enter or leave the Strait of Hormuz," Trump wrote.
"I have also instructed our Navy to seek and interdict every vessel in international waters that has paid a toll to Iran. No one who pays an illegal toll will have safe passage on the high seas," he added.
Trump also warned that "any Iranian who fires at us, or at peaceful vessels, will be blown to hell."
Iran's Revolutionary Guard responded by warning that foreign military vessels approaching the strait would be treated as a breach of the ceasefire and "dealt with harshly and decisively," the Reuters news agency reported.
In an interview with broadcaster Fox News, Trump said he believed Iran would continue negotiations and described the weekend talks as "very friendly."
"I do believe they're going to come to the table on this because nobody can be so stupid as to say 'We want nuclear weapons,' and they have no cards," he said.
Trump also said NATO allies had expressed willingness to support operations in the strait, after previously criticising them for not backing the US-led campaign launched with Israel on February 28, according to Reuters.
The United States and Iran failed to reach an agreement to end their war after 21 hours of talks in Islamabad, Pakistan, the first direct negotiations between the two sides in more than a decade, according to officials.
Each side blamed the other for the collapse of the talks, which were aimed at halting six weeks of fighting that has killed thousands and pushed up global oil prices.
"The bad news is that we have not reached an agreement,” US Vice President JD Vance, who led the American delegation, told reporters. "We’ve made very clear what our red lines are."
Vance said Iran had refused to accept US demands, including a commitment not to pursue nuclear weapons.
"We need to see an affirmative commitment that they will not seek a nuclear weapon and will not pursue the tools needed to quickly achieve one," he said.
Washington and Tehran had agreed on April 7 to a two-week ceasefire shortly before a deadline set by Trump for Iran to reopen the strait..
The agreement followed mediation efforts by Pakistan’s army chief, Field Marshal Asim Munir, and Prime Minister Shehbaz Sharif, according to reports.
Poland has condemned attempts to escalate the conflict in the Middle East and urged all sides to exercise restraint and respect international law.
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Source: Reuters, IAR, PAP