President Donald Trump has sent a letter to Iran's supreme leader Ali Khamenei, urging the negotiation of a new deal on the country's nuclear program. The letter was conveyed on Thursday.

Trump himself revealed the overture in a Friday interview with Fox Business, a first such significant engagement of the administration with Tehran, which is somewhat surprising given Trump's tone regarding Iran has been hawkish, especially on the prior campaign trail. Wide-ranging sanctions are still on the banking, energy, and defense sectors - and have been for years.

"I’ve written them a letter saying I hope you negotiate, because if we have to go in militarily, it’s going to be a terrible thing for them," Trump confirmed to Fox Business’s Maria Bartiromo.

"The other alternative is you have to do something because Iran can't have a nuclear weapon," he followed with, echoing his prior message warning that Tehran can either sign a deal or potentially get bombed.

The International Atomic Energy Agency (IAEA) has described that the Islamic Republic's current stockpile of 60% enriched uranium - if enriched to 90% - would be enough to produce six nuclear bombs.

Trump has recently brought back 'maximum pressure' on Iran, and has even this week advanced the possibility of cracking down on sanctions-busting Iranian oil exports on the high seas, using naval intervention. Clearly this is part of the big stick package of actions meant to push Tehran to the table.

An earlier Fox News interview in February marked the point at which Trump first laid out that Iran has two choices. "Everybody thinks Israel with our help or our approval will go in and bomb the hell out of them," Trump had said at the time while discussing potential Israeli military action against Tehran.

"I would prefer that not happen. I'd much rather see a deal with Iran where we can do a deal, supervise, check it, inspect it," the president continued.

That's when he made one of the more provocative and threatening comments: "There's two ways to stopping them: With bombs or a written piece of paper," he had previously said.

The US is now increasingly worried that given last year's tit-for-tat exchange of major strikes with Israel, Tehran leaders are more incentivized than ever to secretly develop a nuke.

However, the CIA has long assessed, even recently, that Iran's leadership has not yet ordered the pursuit of a bomb. The Ayatollahs throughout the decades have also condemned atomic weapons as 'unIslamic'.

But Iranian leaders have balked at Trump's extended hand. While it's unclear what the reaction will be from the newly sent letter, both the Iranian president and Ayatollah have earlier explained that a perfectly good deal was already in effect - the 2015 JCPOA under Obama - but that Trump unilaterally pulled the US out of it in April 2018.

The Ayatollah has said that Iran simply can't trust Washington to abide by any deal, given any future administration can overturn it, just as Trump did.