JERUSALEM—President Donald Trump’s overtures via a letter to the Islamic Republic of Iran’s supreme leader, Ali Khamenei, to jump-start talks on dismantling Tehran’s illicit nuclear weapons program, were met with rejection by the theocratic state on Sunday, following Trump's latest threat to the regime.

Trump told NBC on Saturday that "If they don't make a deal, there will be bombing," he said. "But there's a chance that if they don't make a deal, that I will do secondary tariffs on them like I did four years ago."

Trump added the U.S. and officials from the Islamic Republic are "talking."

Iran’s President Masoud Pezeshkian said on Sunday "We don’t avoid talks; it’s the breach of promises that has caused issues for us so far," according to the Associated Press. He added, "They must prove that they can build trust." The White House did not immediately respond to Iran's rejection of the talks, the AP reported. 

Pezeshkian still noted that in Iran's response to the letter that indirect negotiations with the Trump administration were still possible.

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The apparent return of Iran’s regime to its standard playbook of opaque indirect talks between the U.S. and Tehran’s rulers raises questions about whether Trump would greenlight military strikes to eradicate Iran’s vast nuclear weapons program. 

After Iran launched two massive missile and drone attacks on Israel last year, Trump could also aid the Jewish state in knocking out Iran’s nuclear weapons apparatus. 

Indirect talks between the U.S. and the world’s worst state-sponsor of terrorism, according to Democratic and Republican administrations, have not compelled Iran to abandon its pursuit of nuclear weapons.

Jason Brodsky, the policy director of United Against Nuclear Iran (UANI), told Fox News Digital that the Iranians "do not want to provide President Trump with a casus belli to strike Iran’s nuclear program. There may be indirect and non-public responses through various intermediaries. I think some Iranian officials perceive a fissure among President Trump’s national security team on Iran. This explains Iran’s foreign minister’s comment in recent days that President Trump’s letter to the supreme leader poses challenges as well as opportunities."

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Brodsky said, "These Iranian officials seek to bypass experienced hands like President Trump’s national security advisor and secretary of state, who have been demanding the dismantlement of Iran’s entire nuclear program in keeping with President Trump’s long-standing and rightful position on this issue, and cultivate individuals around President Trump who do not have experience with Iran or are considered non-traditional conservatives who would be more receptive to their entrees."

Trump promised that "bad things" would happen to Iran if the regime does not come to the table for nuclear negotiations.  "My big preference is that we work it out with Iran, but if we don’t work it out, bad things are gonna happen to Iran," he said on Friday. 

Iran is enriching uranium to 60%, just shy of the 90% weapons-grade. Experts say it could have a nuclear weapon within weeks if it were to take the final steps to building one. Fox News Digital reported in late March that Iran’s regime has enriched enough uranium to manufacture six nuclear weapons, according to a U.N. atomic agency report.

Alireza Nader, an Iranian-American expert on Iran, told Fox News Digital, "Khamenei may be signaling that he’s not interested in negotiations, but his regime desperately needs economic relief. Otherwise, another popular uprising against him could start. Khamenei doesn’t have the cards."

There is widespread discontent among Iranians against the rule of 85-year-old Khamenei.

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Iran’s has upped the ante ever since Trump told FOX Business he sent a letter to Khamenei. Iran has disclosed video footage of its underground "missile city."

Trump also told FOX Business, "I would rather negotiate a deal."

He continued, "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. 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."

Brodsky said, "That means the Islamic Republic may dangle a JCPOA-like deal, with minor modifications from the previous 2015 agreement. Iranian media has been hyping such an arrangement."

In 2018, Trump withdrew from the Obama-negotiated Joint Comprehensive Plan of Action deal because, he argued, that the agreement failed to ensure Iran would not build nuclear weapons and did not codify restrictions against Tehran’s missile program and sponsorship of Islamist terrorism.

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Brodsky said, "These Iranian officials believe they can lure the Trump administration into this arrangement and then President Trump will wave a magic wand and bring the entire Republican Party along with Democrats to support the deal and make it more politically durable than the 2015 JCPOA. This is all despite President Trump’s consistent and strong record in rejecting the JCPOA framework. It reflects desperation in Tehran and a desire to buy time with another failed diplomatic gambit. But it's important to have eyes wide open here as to the games the Iranians will (and are already) playing."

While Trump’s director of national intelligence, Tulsi Gabbard, testified on Tuesday before the Senate Intelligence Committee that the intelligence community "continues to assess that Iran is not building a nuclear weapon and Supreme Leader Khamanei has not authorized the nuclear weapons program he suspended in 2003," she did note that Iran increased its enriched uranium stockpile.

In sharp contrast to U.S. intelligence since 2003, Fox News Digital has previously reported that European intelligence agencies believe Iran is working toward testing an atomic weapon, and sought illicit technology for its nuclear weapons program. 

Counter-proliferation experts, like the prominent physicist and nuclear specialist David Albright, have told Fox News that European intelligence institutions use an updated definition of construction of weapons of mass destruction to assess Iran’s progress in contrast to America’s alleged obsolete definition.

Fox News Digital sent press queries to the U.S. State Department and the National Security Council.

Fox News Digital's Morgan Phillips and the Associated Press and Reuters contributed to this report.