WASHINGTON - US President Donald Trump pilloried the Iran nuclear deal as “insane” Tuesday and threatened “problems” if Tehran restarts controversial programs, exposing a deep rift with European allies.

Hosting French President Emmanuel Macron in the Oval Office, Trump punctured a carefully choreographed display of trans-Atlantic camaraderie with an angry tirade against the three-year old nuclear accord.

The US leader groused that the agreement - inked by the United States, Iran, Europe, Russia and China - does nothing to tackle Tehran’s ballistic missiles program or support for militant groups across the Middle East.

“People know my views on the Iran deal. It was a terrible deal. It should have never ever been made,” Trump railed. “It’s insane. It’s ridiculous.”

The agreement, still backed by Europe, gave Iran massive sanctions relief and the guarantee of a civilian nuclear program in return for curbs on programs that could be used to develop a nuke. It did not tackle western complains about Iran’s ballistic missile programs or support for militant groups across the Middle East.

Trump faces a May 12 deadline to decide on the fate of the accord and is demanding changes that European capitals believe would represent a legal breach.

Iran, meanwhile, has warned it will ramp up enrichment activities if Trump walks away from the accord, prompting Trump to issue a blunt warning.

“They’re not going to be restarting anything. If they restart it, they’re going to have big problems, bigger than they ever had before. And you can mark it down,” he said.

President Emmanuel Macron and his American counterpart called jointly Tuesday for a new nuclear deal with Iran, after the US leader denounced the three-year-old accord as “insane.”

“I can say that we have had very frank discussions on that, just the two of us,” Macron told a joint press conference with Trump at his side. “We, therefore, wish from now on to work on a new deal with Iran.”

“I think we will have a great shot at doing a much bigger, maybe, deal,” said Trump, stressing that any new deal would have to be built on “solid foundations.”

“This is a deal with decayed foundations. It’s a bad deal, it’s a bad structure. It’s falling down,” the US leader said. “We’re going to see what happens on the 12th.”

When asked to clarify if he meant he was pushing for a new accord, or an add-on agreement, Macron said: “I’m not saying that we move from one agreement to another.”

The French president said a new deal would have to include three additional elements: Tehran’s ballistic missile program, its influence across the Middle East, and what happens after 2025 - when under the current accord Iran would be able to progressively restart part of its nuclear program.

President Donald Trump also praised Kim Jong Un as “very open” and “very honorable” on Tuesday, adding the North Korean leader wants to meet “as soon as possible.”

“We are having very good discussions,” Trump said, ahead of a summit with the mercurial Kim expected sometime before the end of June. “He really has been very open, I think — very honorable.”

Meanwhile, a top Iranian official on Tuesday welcomed European powers’ efforts to salvage a historic nuclear deal, but warned they should not simply hand over “a ransom” to US President Donald Trump.

Trump has threatened not to renew the 2015 accord, which curbed Iran’s nuclear programme in exchange for sanctions relief. His threats have prompted pressure from European officials ahead of a May 12 deadline for his decision.

Russia on Tuesday urged a United Nations nuclear disarmament forum to show its support for the “fragile” Iran nuclear accord by signing onto a statement, co-written by China, backing the deal. The head of the arms control unit at Russia’s foreign ministry, Vladimir Yermakov, called on UN members to not “keep silence in hope that the situation will somehow blow over”.

Addressing the preliminary review meeting of the Nuclear Non-Proliferation Treaty (NPT), Yermakov described the landmark 2015 Iran nuclear agreement as “quite a fragile compromise”.

US President Donald Trump has fiercely criticised the complex deal and has threatened to ditch it completely if the signatories do not sign up to tougher measures against Iran.

The president is supposed to waive US sanctions against Tehran by a May 12 deadline to keep the agreement alive but if he refuses to do so, it may unravel.

Russia and China, both supporters of the pact known as the Joint Comprehensive Action Plan (JCPOA), drafted a statement affirming their “unwavering support for the comprehensive and effective implementation” of the deal.

Yermakov urged all nations at the UN nuclear meeting to sign on.

“We believe there is a demand for such a collective message by the (meeting) and hope that the document will find broad support,” he said.

The Russian official then took a thinly veiled shot at Trump’s call to renegotiate the JCPOA in hopes of securing tougher terms.

“Any attempts to amend (the) text for someone’s benefit will inevitably... have powerful negative consequences for regional global stability and security,” Yermakov said.

In his own speech to the forum, Iran’s ambassador to the International Atomic Energy Agency Reza Najafi took on Trump directly, rejecting what he described as Washington’s “ultimatum to certain JCPOA participants for one-sided alterations of the deal’s provisions”.

“Our response to that threat is clear and firm: No, the JCPOA will not be renegotiated or altered,” Najafi said, echoing a stance adopted by Tehran after Trump first raised the prospects of re-visiting a pact negotiated by his predecessor Barack Obama.