President Donald Trump said on Sunday the US Navy would start blockading the Strait of Hormuz, raising the stakes after marathon talks with Iran failed to reach a deal to end the war, jeopardising a fragile two-week ceasefire.
The US Central Command said US forces would begin implementing the blockade of all maritime traffic entering and exiting Iranian ports at 10:00 ET (14:00 GMT) on Monday.
It would be, "enforced impartially against vessels of all nations entering or departing Iranian ports and coastal areas, including all Iranian ports on the Arabian Gulf and Gulf of Oman," a Central Command statement on social media said.
US forces would not impede freedom of navigation for vessels transiting the Strait of Hormuz to and from non-Iranian ports, and additional information would be provided to commercial mariners through a formal notice prior to the start of the blockade, it said.
Trump also said in a post that the US would take action against every vessel in international waters that had paid a toll to Iran, and begin destroying mines that he said the Iranians had dropped in the strait.
"No one who pays an illegal toll will have safe passage on the high seas," Trump wrote, adding: "Any Iranian who fires at us, or at peaceful vessels, will be BLOWN TO HELL!"
Iran's Revolutionary Guards responded to Trump by warning that military vessels approaching the strait will be considered a ceasefire breach and dealt with harshly and decisively, underlining the risk of a dangerous escalation.
Trump said on Sunday that the price of oil and gasoline may remain high through November's midterm elections, a rare acknowledgement of the potential political fallout from the war.
The dollar jumped against other major currencies on Sunday, as investors sought the relative safety of the currency after the talks failed to yield a deal, plunging markets into a seventh week of uncertainty.
(Reporting by Reuters bureaus worldwide, Writing by Idrees Ali, Lisa Shumaker, Raju Gopalakrishnan, Matthias Williams, Keith Weir, Joseph Ax and David Brunnstrom; Editing by William Mallard, Gareth Jones, Alexander Smith, Sergio Non and Deepa Babington)
