Biden Promised to Restore the Iran Nuclear Deal. Now It Risks Derailment.

WASHINGTON — Days before a new hard-line president is set to be inaugurated in Iran, Biden administration officials have turned sharply pessimistic about their chances of quickly restoring the nuclear deal that President Donald J. Trump dismantled, fearing that the new government in Tehran is speeding ahead on nuclear research and production and preparing new demands for the United States.

The concerns are a reversal from just a month ago, when American negotiators, based in part on assurances from the departing Iranian government, believed they were on the cusp of reaching a deal before Ebrahim Raisi, 60, a deeply conservative former head of the judiciary, takes office on Thursday. In June, they were so confident that another round of talks was imminent that a leading American negotiator left his clothes in storage at a hotel in Vienna, where the talks took place through European intermediaries for the past four months.

That session never happened. International inspectors have been virtually blinded. At Iran’s major enrichment site at Natanz, centrifuges are spinning at supersonic speeds, beginning to enrich small amounts of nuclear fuel at near bomb-grade. Elsewhere, some uranium is being turned to metallic form — for medical purposes, the Iranians insist, though the technology is also useful for forming warheads.

It is unclear whether Mr. Raisi will retain the existing Iranian negotiating team or replace them with his own loyalists, who will presumably be determined to show they can drive a harder bargain, getting more sanctions relief in return for temporary limits on Iran’s nuclear activities.

“There’s a real risk here that they come back with unrealistic demands about what they can achieve in these talks,” Robert Malley, the lead American negotiator, said in an interview.

Both sides have much to lose if the diplomacy fails. For President Biden, getting the 2015 nuclear accord back on track is a top goal, in hopes of containing, once more, a nuclear program that has resumed with a vengeance three years after Mr. Trump withdrew from it. It is also critical to Mr. Biden’s effort to restore damaged relations with European allies, who negotiated the original deal, along with the United States, Russia and China.

Mr. Biden’s aides make no secret of their concerns that the Iranians are learning so much from the work now underway that in the near future, perhaps as early as this fall, it may be impossible to return to the old accord. “At that point, we will have to reassess the way forward,” Mr. Malley said. “We hope it doesn’t come to that.”

For years, Mr. Raisi was an advocate of what Iranians call the “resistance economy,” based on the argument that Iran does not need trade with the world and had no need to open up. But during the campaign, he seemed to endorse restoring the deal, perhaps because he was under pressure to show that, unlike his predecessors, he has the skill and toughness to get rid of the American-led sanctions that have ravaged his country’s economy.

Now the economic burdens, worsened by a fifth wave of the coronavirus and water shortages that are partly the result of government mismanagement, have set off violent protests.

The new president will not be the final word on whether the deal is restored. That judgment still belongs to Iran’s supreme leader, Ayatollah Ali Khamenei, who is believed to have lined up the support for Mr. Raisi’s election. And on Wednesday, the ayatollah echoed a key demand: that the United States provide a guarantee that it can never again walk away from the pact the way Mr. Trump did.

“They once violated the nuclear deal at no cost by exiting it,” Ayatollah Khamenei said. “Now they explicitly say that they cannot give guarantees that it would not happen again.”

In fact, Secretary of State Antony J. Blinken and Mr. Malley have said that in a democracy, there is no way to tie the hands of a future president and that the best way to preserve the deal is to show that it is working for both sides. “There is no such thing as a guarantee; that’s not in the nature of diplomacy,” Mr. Malley said. “But we don’t have any intent — the president doesn’t have any intent — of spending all these months negotiating a return to the deal in order to then withdraw.”

But the Iranians have found some sympathy, even among America’s European allies, for their argument, especially among those who fear that if Mr. Biden does not run for a second term, or a Trump-like figure gets elected, the accord could be blown up again.

“If it happened once, it could happen again,” one senior European diplomat involved in the negotiations said.

The new pessimism is a sharp change from a month ago. The departing government, led by President Hassan Rouhani and the foreign minister, Mohammad Javad Zarif, knew their legacies were tied to the nuclear accord they negotiated for more than two years with President Barack Obama and the secretary of state at the time, John Kerry. In Vienna, the Iranians said they believed they had the authority to wrap up talks before Mr. Raisi was inaugurated, so that he could start afresh — and blame anything that went wrong in enforcing the accord on the incompetence of the old government.

Meanwhile, what has happened on the ground in Natanz, and in small research labs around the country, has the United States worried. The most visible problem, though in some ways the easiest to reverse, is that Iran has ratcheted up its production of nuclear fuel over the past two years, and now possesses far more fuel than it did before Mr. Trump pulled out of the agreement. At the time, he declared that Iran would return to the table, begging for a new deal.

It never did while Mr. Trump was in office, and by late last year, according to many reports, he was seeking options from the Pentagon to bomb the country’s nuclear facilities. The Pentagon resisted, and even the biggest Iran hawk in the administration, Secretary of State Mike Pompeo, argued against military action.

If the deal is restored, most of that newly-enriched uranium could be shipped out of the country, which is what happened when the first accord was put together. Far more worrying, officials said, is the scientific knowledge that Iran is steadily gaining by building more advanced centrifuges and experimenting with enriching uranium to 60 percent, just shy of what is needed for a weapon.

“The longer the nonimplementation goes on, the more knowledge we will get,” a senior Iranian official said. “If the U.S. is concerned, the earlier it comes back the better.”

In 2015, the Obama administration was able to claim that if Iran raced to produce nuclear fuel for a bomb — called a “nuclear breakout” — it would take at least a year. That time frame, officials now concede, is down to a few months.

The United States, for its part, has reportedly agreed that if Iran lives by the 2015 accord, more than 1,000 sanctions could be lifted — including on the country’s central bank. Ali Vaez, who directs the Iran project at the International Crisis Group, said the United States still had some space to offer even more sanctions relief, including on some of Ayatollah Khamenei’s close associates, and on some members of the Islamic Revolutionary Guards Corps, which the Trump administration declared a foreign terrorist organization in 2019.

Mr. Vaez said Iran’s insistence that the Biden administration promise to not reimpose sanctions was somewhat understandable. Without it, he said, foreign banks and other businesses will not risk investing in Iran — and thus Tehran would never receive the economic benefits it believes it was promised.

But the Biden administration knows that whatever deal it strikes will be a political problem in Washington. In 2015, all Republicans and a good number of influential Democrats criticized the original accord as insufficiently tough. So there is no way, officials say, they could abandon the threat of “snapping back” sanctions if Iran fails to comply with its part of the bargain.

“The problem is, in reality the U.S. cannot disarm itself of one of the most powerful tools it has in its toolbox of statecraft,” Mr. Vaez said.

And while the talks drag on, the administration is confronting another reality: For the first time in years, international inspectors have very little idea of what is happening in the underground Natanz plant.

The inspection teams have been barred from many facilities they once regularly visited, measuring enrichment levels and accounting for every gram of material produced. An agreement to keep cameras and sensors running lapsed in June.

The Iranians suggest access to the equipment will be restored when an accord is reached, but there is no guarantee that inspectors will have access to the back footage.

A month ago, Mr. Blinken said that the agreement’s lapse was a “serious concern” that “needs to be resolved.”

The Iranians ignored the warning.

David E. Sanger and Lara Jakes reported from Washington, and Farnaz Fassihi from New York.