President Trump warned former Secretary of State John Kerry to “stay away” from Iran negotiations ahead of his crucial Tuesday afternoon announcement, where he will reveal whether the U.S. will preserve the Obama-era nuclear deal with Tehran.

The president’s tweet comes as he prepares to tell the world his administration’s plan for the future of the Iran pact. Ahead of a May 12 deadline, Trump tweeted that he would make the announcement at 2 p.m. ET on Tuesday.

He is widely expected to re-impose sanctions, a move that could unravel the agreement, but has not yet said publicly what he will decide.

The president’s latest swipe at Kerry comes amid reports that the former secretary of state had meetings with foreign leaders in a bid to save the deal, practicing what Trump has called “possibly illegal shadow diplomacy.”

“John Kerry can’t get over the fact that he had his chance and blew it! Stay away from negotiations John, you are hurting your country!” Trump tweeted early Tuesday.

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Kerry reportedly met with Iranian Foreign Minister Javad Zarif in recent months. Kerry reportedly also spoke with German President Frank-Walter Steinmeier, who was foreign minister of Germany when the deal was negotiated; French President Emmanuel Macron; and European Union foreign affairs chief Federica Mogherini.

A spokesman for the United Nations secretary-general said Monday he was “not aware of any meetings,” but in a statement to Fox News, a spokesman for Kerry seemingly admitted the discussions.

“I think every American would want every voice possible urging Iran to remain in compliance with the nuclear agreement that prevented a war. Secretary Kerry stays in touch with his former counterparts around the world just like every previous Secretary of State,” the Kerry spokesman told Fox News in an email on Monday. “Like America’s closest allies, he believes it is important that the nuclear agreement, which took the world years to negotiate, remain effective as countries focus on stability in the region.”

Under the 2015 nuclear deal struck by the United States under the Obama administration, world powers, and Iran, sanctions against Tehran were lifted in exchange for Iran’s cooperation in restricting its nuclear program. If the deal collapses, Iran would be free to resume its nuclear activities.

According to The Washington Post, Trump is expected to announce that he will not continue a waiver of sanctions against Iran. Trump’s move could re-impose strong sanctions on Tehran, which could lead to retaliation from the Iranian regime—which has warned the U.S. of “grave” consequences should it withdraw.

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Iran’s parliamentary speaker was quoted saying on Tuesday that the end of the accord will spark more unity and support for the Islamic Revolution among Iranians.

“Mr. Trump…Rest assured that this loyalty in nuclear issue will [encourage] the great Iranian nation to continue on the path of the Islamic Revolution firmly behind the leadership of its supreme leader,” Ali Larjani reportedly said.

But Iranian president Hassan Rouhani said Tuesday that if the U.S. scraps the deal, there could be immediate difficulties -- but remained hopeful that the country would recover.

“It is possible that we will face some problems for two or three months, but we will pass through this,” Rouhani said at a petroleum expo in Tehran on Tuesday.

Rouhani did say this week though, that if the U.S. pulls out, Iran could stick with the European Union, whose economies do more business with Iran than the U.S.

Iranian President Hassan Rouhani has warned the U.S. of "grave" consequences should President Trump decide to withdraw from the nuclear deal. (AP)

The deal is composed of sanctions, written agreements and staggered deadlines, so Trump has several ways to pull the U.S. out of the deal by renegotiating and scrapping some commitments.

Trump could impose sanctions on Iran’s central bank, targeting oil exports, then would give those doing business with Iran a six-month grace period to wind down business and avoid running into problems with the sanctions. Waivers on those sanctions must be signed every 120 days, which Trump has done thus far in his administration.

Fox News’ Lukas Mikelionis, Ben Evansky and The Associated Press contributed to this report.