Donald Trump continues to lash out at former Secretary of State John Kerry for trying to interfere with foreign policy as the president prepares to make a major announcement about the Iran nuclear deal.

'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 Tuesday.

Trump will make his intentions toward Tehran known Tuesday afternoon, and is likely to end the sanctions relief that has breathed new life into Iran's economy – and, Republican critics of the Obama-era agreement say, allowed the Islamist nation to quietly advance the nuclear weapons program it swore to stop in its tracks.

The president blasted Kerry on Monday following news reports that the ex-diplomat had secretly met with foreign governments in a bid to save the much-maligned deal.

The multinational bargain, which Trump has called 'insane' and 'the worst deal ever,' called for a decade-long pledge from Iran to cease developing nuclear weapons, in exchange for a relaxation of international sanctions.

President Donald Trump went back on offense against John Kerry on Tuesday, blasting him for interfering in foreign policy

Trump slapped the ex-diplomat for meeting in secret with foreign leaders in order to try and salvage the Iran nuclear deal that Barack Obama inked in 2015

Kerry met with leaders from Iran, Germany, France and the European Union despite the fact that he no longer has any legal authority to conduct foreign policy

If the sanctions snap back into effect, the U.S. will be in violation of the agreement and effectively end its participation. Iran could then decide to walk away from it entirely and resume its nuclear weapons program in the open – with the benefit of $150 billion in assets the Obama White House unfroze.

The Boston Globe reported Friday that Kerry quietly met two weeks ago with Iranian Foreign Minister Javad Zarif, and had separate confabs with German President Frank-Walter Steinmeier and French President Emmanuel Macron – all to strategize against Trump's intention to upend the deal.

'The United States does not need John Kerry’s possibly illegal Shadow Diplomacy on the very badly negotiated Iran Deal,' the president wrote Monday on Twitter. 'He was the one that created this MESS in the first place!'

Kerry brokered the deal for the Obama administration. Trump has threatened to reimpose sanctions by May 12, the deadline for certifying Iran's compliance with its obligations under the arrangement.

Trump tweeted Monday that he would announce his position on the Iran accord less than a day later, surprising even his closest communications aides

Trump too a shot at Kerry on Monday for conducting 'shadow diplomacy' behind his back that undermines his negotiations with Iran over rewriting the multinational nuclear deal

Trump on Monday called Kerry's intervention 'possibly illegal' and blamed him for the current arrangement that gave Tehran sanctions relief but would allow it to build nuclear bombs as soon as 2027

Kerry (left) is seen with Iranian Foreign Minister Mohammad Javad Zarif in 2016; Kerry met with Zarif last month for secret talks about how to undermine Trump's bid to kill the nuclear deal

White House Press Secretary Sarah Sanders told reporters on Monday that Kerry's advocacy won't make a difference as Trump weighs what to do.

'I don't think that we would take advice from somebody who created what the president sees as one of the worst deals ever made,' she said.

'I don't see why we would start listening to him now.'

A spokesman for Kerry issued a statement late Monday morning, defending his apparent habit of lobbying foreign governments as a civilian.

'I think every American would want every voice possible urging Iran to remain in compliance with the nuclear agreement that prevented a war,' the statement said.

'Secretary Kerry stays in touch with his former counterparts around the world just like every previous Secretary of State. 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.'

But whether or not Kerry's flurry of clandestine diplomacy bears fruit, he will be criticized for carrying out the duties of the job he lost when Trump became president.

A federal law called the Logan Act makes it a felony for unauthorized civilians to conduct foreign policy with nations that are in the midst of a dispute with the United States.

Kerry has also been meeting with German President Frank-Walter Steinmeier (left) and French President Emmanuel Macron (right) in attempts to salvage the Iran deal

Kerry could run afoul of the Logan Act, a 200+ year-old federal law that made it a felony for civilians to conduct foreign policy without authorization

The statute, known as the Logan Act, dates back to 1799 and has only been used twice to indict people – in 1803 and 1852. Neither was convicted.

One defendant, a Peruvian admiral, was prosecuted for writing a letter to the president of Mexico to scuttle a competitor's bid to build a railroad connecting the Atlantic and Pacific Oceans.

The other was a farmer charged with the crime of writing a newspper article urging western U.S. states to secede and join neighboring French territories.

Some legal scholars have written that the Logan Act is unconstitutional, and only remains on the books because it hasn't been tested in court.

Some of Trump's own advisers were accused of violating the Logan Act during the post-election transition period in 2016 and 2017.

Michael Flynn, Trump's first national security adviser who was fired after just weeks on the job, was originally eyed as a possible Logan Act violator when the Justice Department targeted him.

Flynn had made contact with Russia's then-ambassador to the U.S. Sergey Kislyak to discuss how the new administration might view existing sanctions regimes imposed on Moscow, and how Trump's team hoped the Kremlin would vote on a pending United Nations resolution condemning Israel.

Sally Yates, then the deputy attorney general, later testified that the potential for Logan Act violations was the initial justification for interrogating Flynn – who later pleaded guilty to lying to the FBI in connection with that grilling.

Kerry, at one time a Democratic senator for Massachussets, has been accused of violating the Logan Act in the past.

In January he told a confidant of Palestinian Authority President Mahmoud Abbas that he should 'stay strong' and 'play for time' while Trump is in the White House.

Kerry told the Lebanese academic Hussein Agha that he was considering a second run for the White House in 2020, and aimed to help Palestinians in their territorial battles with Israel.

'It is unusual for a former secretary of state to engage in foreign policy like this, as an actual diplomat and quasi-negotiator,' Michael O'Hanlon, a foreign policy expert at the Brookings Institution, told the Globe, referring to Kerry's Iran efforts this year.

'Of course, former secretaries of state often remain quite engaged with foreign leaders, as they should, but it's rarely so issue-specific, especially when they have just left office.'

Israeli President Benjamin Netanyahu has been pushing Trump to take a more aggressive posture toward Iran, his nation's most prolific antagonist.

Netanyahu delivered a presentation last week claiming Israel's intelligence agency had proof that Iran 'lied' about its intention to dismantle its nuclear weapons program.