President Donald Trump said he sent a letter to Iran’s Supreme Leader Ayatollah Ali Khamenei about negotiating a nuclear deal, while also threatening military action if an agreement isn’t reached.

Trump said he sent the letter on Wednesday during an interview with Fox Business, a clip of which was released by the network on Friday.

“There are two ways Iran can be handled, militarily or you make a deal. I would prefer to make a deal,” Trump told Fox News host Maria Bartiromo.

“I would rather negotiate a deal. I’m not sure that everybody agrees with me, but we can make a deal that would be just as good as if you won militarily,” Trump said. “But the time is happening now, the time is coming up. Something is going to happen one way or the other. I hope that Iran, and I’ve written them a letter, saying I hope you’re going to negotiate because if we have to go in militarily it’s going to be a terrible thing for them.”

The Permanent Mission of the Islamic Republic of Iran to the United Nations, however, said they have not received a letter from Trump.

“We have not received such a letter so far,” the mission said in a statement.

Fox’s Bartiromo asked the president if he was giving Iranian leadership an ultimatum.

“No I didn’t say, ‘You better.’ I said, ‘I hope you’re going to negotiate,’ because it will be a lot better for Iran. I think they want to get that letter. The other alternative is we have to do something because you can’t let them have a nuclear weapon,” Trump warned.

This isn’t the first time Trump has sent a message to Khamenei. In 2019, with the help of former Japanese Prime Minister Shinzo Abe, he sent a similar message, but the Iranian leader publicly rejected that offer to talk.

Khamenei reportedly said at the time, “I do not consider Trump as a person worth exchanging any message with.”

Trump’s comments proposing a nuclear deal come after he withdrew the U.S. from an agreement reached between Iran and the Obama administration during his first term in office. That nuclear deal, established in 2015, allowed Iran to enrich uranium only up to 3.67% purity and maintain a stockpile of uranium of 300 kilograms.

Last month, Trump signed a memorandum that seeks to exert “maximum pressure” on Iran, including pushing its oil exports down to zero in order to stop Tehran from possessing nuclear weapons capability.

“I’m going to sign it, but hopefully we’re not going to have to use it very much. We will see whether or not we can arrange or work out a deal with Iran,” he said.

Asked about what kind of deal he’d like to see, Trump responded: “We’re going to see. They cannot have a nuclear weapon. With me, it’s very simple: Iran cannot have a nuclear weapon.”

As he spoke on the issue in the Oval Office, Trump also said he’s left instructions to “obliterate” Iran if they ever carried out an assassination.

Ellie Kaufman contributed to this report.