Earlier on Monday, after Iranian authorities said there were no talks under way, Trump criticised what he called Iran's "unbelievably duplicitous" leadership.
Trump, speaking at the Oval Office, said he expected negotiations will reopen the Strait of Hormuz and create a pathway for Iran to address United States' concerns about its nuclear program.
The president said the "first phase is the opening of the straits. The second phase will be the denuclearisation".
Trump said that "will take a little while".
"They are going on right now," Trump told reporters when asked about the status of the negotiations, saying the two sides were talking at the request of Iran, Saudi Arabia, the United Arab Emirates and Qatar among others.
"This is a last chance for them to sign a good document," he said, referring to Iran.
Trump has threatened to escalate attacks on Iran only to edge away from his threats several times since the start of US and Israel strikes on February 28.
Asked by a reporter how the US public view him repeatedly making grim threats on Iran before backing away, Trump responded that he was showing patience out of a consideration for Iranian life.
"I want to give them every last chance before decapitation," Trump said.
He added, "Hopefully, they'll come to their senses."
Iranian foreign ministry spokesman Esmaeil Baghaei had said earlier on Monday that Iran was negotiating with Oman over a joint temporary shipping corridor in the Strait of Hormuz, according to comments carried by state news agency IRNA.
Baghaei said the talks only involved Iran and Oman, stressing that Iran was currently not involved in negotiations with the US.
Issues relating to Iran and the US should be examined in the coming phases in order to assess how the situation may develop, he said.
with AP and DPA
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