Trump has threatened to take out Iran "in one night" if it fails to make a deal before the deadline he set for Tehran to reopen the Strait of Hormuz, a critical global energy route.
U.S. President Donald Trump's deadline for an "acceptable" deal—one that includes the free flow of energy through the Gulf—is set for 20:00 Washington DC time on Tuesday, April 7 (00:00 GMT Wednesday).
Speaking at the White House, Trump said that he believed "reasonable" leaders in Iran were negotiating in "good faith," but the outcome remained uncertain.
Iran has rejected proposals for a temporary ceasefire, instead calling for a permanent end to the conflict and the lifting of sanctions.
Trump says, 'Iran would be send to 'Stone Ages'
Once the deadline passes, Trump added, Iran would be sent back to the "Stone Ages."
"They're going to have no bridges," he said. "They're going to have no power plants."
Despite Iran's earlier rejection of US demands, Trump continued to express optimism that Iran was negotiating in good faith after successive layers of Iranian leadership were killed in US and Israeli strikes.
"We're going to find out," he said.
Whereas meaningful progress in any negotiation is unlikely to take place without a ceasefire first, as the officials said that talks were complicated because of difficulties in getting messages to and from Iranian officials amid an ongoing communications blackout.
Pakistan, Turkey, and Egypt have all been involved in efforts to mediate, but Iran rejected a 'temporary' ceasefire.
Meanwhile, legal experts have warned that deliberate, sustained assaults on Iranian infrastructure could constitute a war crime.
"Obliterating all power plants and threatening coercive actions against the civilian population to try to bring a government to the negotiating table—those kinds of things are all flatly illegal," Tess Bridgeman, former Obama-era National Security Council legal advisor, told CBS.
Earlier in the day, Trump said he was not "worried" about that possibility and in the news conference insisted that Iran's population would be "willing to suffer to have freedom"—even if toppling Iran's government was not his intention.
The president also renewed his criticism of key US allies—including the UK, NATO, and South Korea—that he said had failed to come to the help of the US during the conflict.
"That's a mark on NATO that will never disappear," he said, adding that the US does not "need" the UK.
American forces have conducted over 13,000 strikes across Iran since the war began, according to an update from the US military's Central Command on Monday.
Trump said, without providing evidence, that the U.S. has "numerous intercepts" from Iranian civilians urging it not to let up in trying to dislodge the Iranian government from power.
"They would be willing to suffer that in order to have freedom," Trump said.
