U.S. President Donald Trump said Monday that talks with Iran “are going on right now,” calling them Tehran’s “last chance” to sign a deal with Washington and saying the Strait of Hormuz could reopen as soon as Tuesday.

Speaking to reporters at the White House, Trump said the talks were taking place at Iran’s request and after appeals from Gulf allies, including Saudi Arabia, the United Arab Emirates and Qatar. “Many countries called,” he said, adding that “this is the last chance for them to sign a good document.”

Trump did not provide details on where or when the talks would take place. “You’ll find out today or tomorrow,” he said when asked about the location of possible discussions. “They’re going to go quickly one way or the other. It’s not very complex.”

Trump said reopening the Strait of Hormuz would be the first phase of any agreement, followed by Iran’s denuclearization. “The first phase is the opening of the straits. The second phase will be the denuclearization,” he said, adding that the latter “will take a little while.” He also warned that he would not allow Iran to control passage through the strategic waterway, saying he would not let Tehran “charge to go through Hormuz.” He added that the strait could be opened “literally by tomorrow.”

Asked what had changed this time after he previously called off planned strikes on Iran, Trump said: “I want to give them every last chance before decapitation.”

Earlier Monday, Iran said no direct talks with Washington were underway, after Trump accused Tehran’s leadership of being “unbelievably duplicitous.”