Iran nuclear talks have resumed in Vienna. Here’s what to know about the negotiations.

Iranian chief nuclear negotiator Ali Bagheri Kani leaves the venue of talks aimed at reviving the Iran nuclear deal in Vienna on Dec. 3. (Joe Klamar/AFP/Getty Images)
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The eighth round of talks in Vienna aimed at reviving the Iran nuclear deal adjourned in late January amid what European diplomats called “the final stage” in negotiations — but major points of contention remain between Washington and Tehran, while negotiators warn that Iran’s nuclear program is weeks away from advancing far beyond the 2015 accord’s parameters.

Since early last year, Iran and world powers — including Britain, France, Germany, Russia and China — have met to discuss the future of the Joint Comprehensive Plan of Action (JCPOA), which had curbed Iran’s nuclear activities in exchange for sanctions relief. President Donald Trump unilaterally withdrew in 2018, reimposing a near-total embargo on Iran. Unlike in 2015, Washington has not directly participated in the talks, and instead has communicated with Tehran via European intermediaries.

In early January, U.S. State Department spokesman Ned Price said the parties had made “modest progress,” comments echoed by the French Foreign Ministry. Other countries such as Israel singled that they think a new accord could soon be reached.

The tone has shifted somewhat since early December, when negotiations adjourned amid an impasse, leaving a major breakthrough more distant than ever. The International Atomic Energy Agency, which is responsible for monitoring Iran’s nuclear program, said that Tehran was using advanced centrifuges to enrich uranium to 20 percent purity at Fordow, its most heavily guarded enrichment facility. Iranian negotiators had also presented the signatories with a set of maximalist demands, rolling back progress Western diplomats said was made earlier in the year.

But diplomats have described this latest round of talks as the most intensive yet, with just a narrow list of differences now determining whether a deal will proceed or not.

“If a deal is not reached in the next few weeks, Iran’s ongoing nuclear advances will make it impossible to return to the JCPOA,” Secretary of State Antony Blinken said in late January. “But right now, there’s still a window, a brief one, to bring those talks to a successful conclusion and address the remaining concerns of all sides.”

Here’s what you need to know about the Iran nuclear deal and the obstacles to reviving it.