Iranian President Hassan Rouhani makes a speech during a ceremony in Tehran, Iran on January 10, 2019. Anadolu Agency | Anadolu Agency | Getty Images

DUBAI — Iran could be playing with fire as it threatens to ditch its commitments to the 2015 Iranian nuclear deal, officially known as the JCPOA (the Joint Comprehensive Plan of Action), in the face of crippling U.S. sanctions. If Europe does not step in to protect Iran from those sanctions, salvaging trade with its oil and banking sectors in violation of U.S. rules, Tehran says it will return to higher levels of uranium enrichment, which would potentially pave the way for bomb-making capabilities. But how close is the Islamic Republic to having a bomb? How real is the threat? Richard Nephew, who served as the State Department's lead sanctions expert for negotiations with Iran from 2013 to 2014, doesn't see an imminent nuclear threat. Rather, he told CNBC, this turn of events heralds a slower but no less dangerous march in that direction. "This is not a decision that will lead Iran to build a bomb. But it foreshadows a really severe escalation path, especially the 60-day threat to ramp up enrichment levels and work on the Arak reactor," Nephew told CNBC.

60 days to find a solution

Iranian President Hassan Rouhani announced Wednesday that the country would break off some key commitments to the 2015 nuclear deal that had kept caps on its nuclear activities, giving EU leaders 60 days to negotiate a solution. The deal, enacted under the Obama administration, was meant to lift sanctions on Iran in exchange for limits to its nuclear program, until the U.S. withdrew from it last year under the direction of President Donald Trump.

That's my chief worry: the threat and counter threat dynamic that leaves no one with room to climb down. Richard Nephew Former lead sanctions expert, U.S. State Department

Iran's announced breaches include keeping its unspent enriched uranium instead of selling it, which would increase its stockpile of feedstock for nuclear reactors, and restarting construction on its Arak nuclear reactor, which was capable of producing weapons-grade plutonium — activities both halted under the nuclear deal. If carried out, those actions could prompt aggressive countermeasures from the U.S. or Israel, former diplomats told CNBC. "That's my chief worry," Nephew, now a senior fellow at the Brookings Institute, added. "The threat and counter threat dynamic that leaves no one with room to climb down and, to be contrary, seems certain to increase the chance of full Iranian nuclear restart."

'This is a serious threat'

Henry Rome, Iran analyst at risk consultancy Eurasia Group, sees a similar opening for greater escalation and confrontation between the U.S. and Iran. The developments from Tehran "do not immediately bring (Iran) closer to a nuclear weapon," Rome said in a research note Wednesday. "But Iran's decision to openly chip away at its nuclear commitments marks the beginning of a new and concerning dynamic between the U.S. and Iran that is ripe for miscalculation." The 60-day threat is what concerns Rome and Nephew the most: Iran has proposed exceeding its JCPOA enrichment cap of 3.67%, which is the amount allowed for civilian nuclear power development. Weapons-grade enrichment is 90%, but according to nuclear experts, reaching 3 to 4% enrichment equates to roughly two-thirds of the work done toward that 90% figure, as any increases beyond that seemingly small amount disproportionately speed up breakout time. "This is a serious threat," Rome said.

Experts including Anne Harrington, a lecturer in international relations at Cardiff University with a focus on nuclear nonproliferation, puts the current breakout time for Iran reaching bomb-making capability at one year.

Europe 'rejects any ultimatums'

EU leaders, for their part, promptly responded Thursday by saying they "reject any ultimatums" but remain committed to the deal. Iran now finds itself in a high-stakes gamble, where it could very well lose all goodwill from Europe while providing Washington justification for harsher action and even military strikes. Iranian officials have stressed that their move is legal and reversible, emphasizing the two-month window for diplomatic action. A spokesman for Iran's atomic energy agency said Thursday that the country wants to bring the nuclear deal "back on track."