The United States and Iran each say they control the Strait of Hormuz after attacks over the weekend stretching across the wider Middle East.
Iranian state media reported explosions, including in the port city of Bandar Abbas on the strait and in Sirik, another southern coastal city.
Trump threatened to strike Iran’s civilian infrastructure, including electric plants and desalinization plants, and to seize Kharg Island.
The cancellation of talks raised questions about an initial agreement to end the war in Iran.
The U.S. agreement to immediately allow Iran to sell its oil freely and the offer to eventually lift all sanctions.
The crash occurred with the Middle East still reeling after Iran and Israel exchanged fire the previous day.
The deal would extend the ceasefire by 60 days and reopen the Strait of Hormuz as new talks are held on Iran’s disputed nuclear program.
Iran and the United States have reached an impasse again over how to end their war. Their ceasefire is growing increasingly shaky.
The blockade, announced by U.S. Central Command, will affect vessels entering or leaving Iranian ports.
Trump has warned Iran that the U.S. could set the country 'back to the stone ages,' including targeting power plants and bridges.