A day after sounding conciliatory and suggesting a deal could be reached this week, Trump wrote on his Truth Social network that the United States is in "serious discussions" with "a more reasonable regime" in Tehran. But he added an ominous warning.

"Great progress has been made but, if for any reason a deal is not shortly reached, which it probably will be, and if the Hormuz Strait is not immediately 'Open for Business,' we will conclude our lovely 'stay' in Iran by blowing up and completely obliterating all of their Electric Generating Plants, Oil Wells and Kharg Island (and possibly all desalinization plants!), which we have purposefully not yet 'touched,'" Trump said.

On Sunday night, Trump told reporters on Air Force One that the United States had achieved "regime change" in Iran through the war launched a month ago with Israel, citing the number of Iranian leaders who have been killed. He called the new leadership "much more reasonable".

"We're dealing with different people than anybody's dealt with before. It's a whole different group of people. So I would consider that regime change."

Asked whether there could be an agreement with Iran this coming week, Trump said: "I do see a deal in Iran. Could be soon."