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Iranian women chant slogans during an anti-US demonstration outside the former US embassy headquarters in the capital Tehran on May 9, 2018. - Iranians reacted with a mix of sadness, resignation and defiance on May 9 to US President Donald Trump's withdrawal from the nuclear deal, with sharp divisions among officials on how best to respond.
For many, Trump's decision on Tuesday to pull out of the landmark nuclear deal marked the final death knell for the hope created when it was signed in 2015 that Iran might finally escape decades of isolation and US hostility. (Photo by ATTA KENARE / AFP)        (Photo credit should read ATTA KENARE/AFP/Getty Images)
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Iranian women chant slogans during an anti-US demonstration outside the former US embassy headquarters in the capital Tehran on May 9, 2018. - Iranians reacted with a mix of sadness, resignation and defiance on May 9 to US President Donald Trump's withdrawal from the nuclear deal, with sharp divisions among officials on how best to respond. For many, Trump's decision on Tuesday to pull out of the landmark nuclear deal marked the final death knell for the hope created when it was signed in 2015 that Iran might finally escape decades of isolation and US hostility. (Photo by ATTA KENARE / AFP) (Photo credit should read ATTA KENARE/AFP/Getty Images)
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Iranian lawmakers burn two pieces of papers representing the U.S. flag and the nuclear deal as they chant slogans against the U.S. at the parliament in Tehran, Iran, Wednesday, May 9, 2018. Iranian lawmakers have set a paper U.S. flag ablaze at parliament after President Donald Trump's nuclear deal pullout, shouting, "Death to America!". President Donald Trump withdrew the U.S. from the deal on Tuesday and restored harsh sanctions against Iran. (AP Photo)
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ISFAHAN, IRAN - MARCH 30:  A worker walks inside of an uranium conversion facility March 30, 2005 just outside the city of Isfahan, about 254 miles (410 kilometers), south of capital Tehran, Iran. The cities of Isfahan and Natanz in central Iran are home to the heart of Iran's nuclear program. The facility in Isfahan makes hexaflouride gas, which is then enriched by feeding it into centrifuges at a facility in Natanz, Iran. Iran's President Mohammad Khatami and the head of Iran's Atomic Energy Organisation Gholamreza Aghazadeh is scheduled to visit the facilities. (Photo by Getty Images)
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Washington CNN —  

President Donald Trump warned Iran of “severe consequences” if it restarted its nuclear program, one day after he announced the US would withdraw from the Iran nuclear deal, which has kept Tehran from developing its atomic program.

Asked what he would do if Iran restarted its program, Trump said: “I would advise Iran not to start their nuclear program.”

“If they do, there will be very severe consequences,” the President said Wednesday during a Cabinet meeting.

Trump announced Tuesday he is quitting the Iran nuclear deal, pitting him against the United States’ closest allies and leaving the future of Tehran’s nuclear ambitions in question.

“We will not allow American cities to be threatened with destruction,” Trump said Tuesday from the White House Diplomatic Room, despite the fact that Iranian missiles cannot reach the US. “Today’s action sends a critical message: The United States no longer makes empty threats.”

He went on to say, “If the regime continues its nuclear aspirations, it will have bigger problems that it has ever had before.”

Trump’s decision and his threats to Iran raise questions about what legal grounds the US can use to enforce Iranian compliance now that it has walked away from the international pact, and whether the President is gunning for a confrontation.

Wendy Sherman, a former undersecretary of state for political affairs and former negotiator with North Korea, said Iran would not have to continue with its obligations after a US withdrawal. “It’s not required to,” Sherman told reporters during a call organized by the group National Security Action.

“If the United States falls out of compliance with the deal, then it is up to every other member of the deal to decide how they want to proceed,” Sherman said.

Iran’s President Hassan Rouhani said Tuesday that he was ordering the country’s atomic industry to be ready to restart industrial scale enrichment of uranium, but other officials indicated Iran intends to continue sticking with the deal.

At a Tuesday meeting between European and Iranian officials in Brussels, Iran said it would stay in the deal if the Europeans could keep their own financial commitments and also make up for the loss Tehran would face as a result of the new US sanctions, according to a European diplomat.

Iran’s foreign minister, Javad Zarif, tweeted Tuesday that he would spearhead that diplomatic effort, adding, “outcome will determine our response.”

Some analysts pointed to the disconnect in Trump’s remarks – demanding adherence to the terms of a deal he’d just quit – as well as his threats to Iran and warned that the President may be spoiling for a fight.

“That’s the posture you take when you’re looking for confrontation,” said Trita Parsi, president of the National Iranian American Council.

He pointed to the appointments of national security adviser John Bolton, who has called for regime change in Iran, and Secretary of State Mike Pompeo, who advocated for military strikes on Tehran during talks on the nuclear deal.

“Bolton has been extremely explicit about his desire for a military confrontation,” Parsi said. “What I think the Trump administration is doing is putting the pieces into place to have a major confrontation with Iran.”

In announcing his long-telegraphed decision, Trump said he would initiate new sanctions on the regime, crippling the touchstone agreement negotiated by his predecessor. Trump had said any country that helps Iran obtain nuclear weapons would also be “strongly sanctioned.”

“This was a horrible one-sided deal that should have never, ever been made,” the President said Tuesday in remarks that, at times, misrepresented the international agreement’s provisions. “It didn’t bring calm, it didn’t bring peace, and it never will.”

Trump’s decision could have explosive consequences, straining long-standing US alliances, disrupting oil markets and boosting tensions in the Middle East, even if the US reversal doesn’t lead Iran to restart its atomic program.

While Trump supporters praised the move, analysts and critics said it undermines Washington’s credibility in future negotiations – particularly with North Korea – and potentially empowers the very hardliners in Iran that Trump vilified in his remarks.

It also further isolates Trump on the global stage, where he has angered even the staunchest US allies by reneging on US commitments to the Paris climate accord and pulling out of the Trans-Pacific Partnership trade agreement.

CNN’s Elise Labott contributed to this report.