Talks to revive the Iran nuclear deal begin again Monday in Vienna. It'll be the seventh round of meetings between the United States, Iran, European powers and China but the first in nearly six months.

And a lot has happened since the last round to raise the stakes for any deal.

To recap, the 2015 deal gave Iran relief from economic sanctions in return for limits on its nuclear program. President Trump abandoned the agreement in 2018, reimposing the sanctions the U.S. had lifted. Iran responded with a public, step-by-step ramping up of the machinery used to enrich uranium — the nuclear fuel needed for a bomb.

Iran and the U.S. — along with the other world powers involved in the deal — say they want to restore it. But they've been stuck on who takes the first steps.

Since the talks stalled, Iran has elected a new, hard-line president who's heightened his country's demands for any new agreement. And in the background, there's been a series of attacks on Iran's nuclear program, suspected to originate in Israel, including the assassination of a leading Iranian scientist a year ago. That raises the risk of conflict at the bargaining table.

Both the U.S. and Iran are out of compliance with the deal right now

The Trump administration argued that the agreement worked out by the Obama White House was too short — parts of it expire in 2025 — and should have required fundamental changes in Iran's policies. When Trump reimposed sanctions, he cut off most of Iran's oil sales. When other partners in the deal — the European Union, China, Russia — objected, the U.S. threatened that any company doing business with Iran would also be cut off from business with the U.S. Most of those sanctions are still in place and Iranians feel the economic pain. That's leverage for Biden's negotiators now.

In response to the U.S. exit, Iran methodically broke the deal's limits — its conservative parliament even passed a law to require those breaches. The country has since stockpiled more enriched uranium than the deal allows. And it has enriched its supply well beyond the levels stipulated in the deal, that is, closer to the levels of enrichment needed for a weapon.

Back when the U.S. was in the deal and Iran was complying with it, analysts said its program was frozen and at least a year away from making enough enriched uranium needed for a bomb. Now, experts say it could be a month away if Iran wanted to go for it. (But making an actual bomb, testing it and loading it on missiles could take a year or two.) Perhaps most troubling, Iran has restricted access to inspectors from the International Atomic Energy Agency, an atomic watchdog that monitors its nuclear sites. They could be missing out on vital information.

To get back in the deal, the U.S. would need to unspool the complicated web of sanctions. Iran would have to open up again to inspectors, dismantle equipment, and ship out uranium or reduce its levels of enrichment. Either way, Iran has already learned more about how to make a nuclear weapon in the process.

Iran has new leadership sounding a harder bargaining position

Amid resentment over the country's poor economy and disappointment in the collapse of the deal, Iranians elected President Ibrahim Raisi in June. He's more of a hard-liner than his predecessor, Hassan Rouhani, who had agreed to the deal in 2015. Raisi seems determined to show he can get a better deal for his people.

The man expected to lead the negotiations for Iran recently said these shouldn't even be called, "nuclear talks." He claims they're about sanctions. "We do not have nuclear talks," Iranian Deputy Foreign Minister Ali Bagheri Kani told state media, "because the nuclear issue was fully agreed in 2015."

Iranian officials say, basically, that since it was the U.S. that first broke the deal, it should be the U.S. that makes the first moves to get it going again by lifting all the sanctions. And, burned by Trump's withdrawal, they say they want a guarantee the deal will remain in force even after the next U.S. presidential election — a promise probably not possible under the U.S. system.

The Biden administration wants a deal, but it won't wait much longer

U.S. officials see the new posturing on the other side and say it's up to Iran to prove it's interested in a deal. Speaking to NPR last week, U.S. negotiator Robert Malley tempered expectations. "If [Iran is] dragging their feet at the negotiating table, accelerating their pace with their nuclear program, that will be their answer to whether they want to go back into the deal," Malley said. "And it will be a negative one if that's what they choose to do."

He's urged Iran to at least meet directly with the U.S., which it refuses. He and European leaders have called on Iran to stop breaking the terms of the deal. Malley told NPR that if Iran doesn't return to the deal, the U.S. would need "other efforts, diplomatic and otherwise, to try to address Iran's nuclear ambitions." He said Iran's nuclear advances could soon make it too late for a deal. "We don't have much time before we have to conclude that Iran has chosen a different path," he said.

At times, the U.S. has also raised the idea adding new conditions to the deal — including possibly extending the term of the agreement or trying to include limits on Iran's ballistic missile program. Iran says those are non-starters.

Supporters of a deal say it would curb Iran's nukes. Opponents say it would let Iran skate on missiles and militants

Proponents of re-entering the deal say it keeps Iran from getting close to making a bomb. Even Trump's defense secretary said Iran was in compliance back when the deal was in effect. Backers of an agreement say other issues with Iran — like its support for militants, human rights violations, threats against Israel and Saudi Arabia — can be managed separately and more easily if the country doesn't pose a nuclear threat.

Opponents to the deal say the Iranian regime is shaky and hurting from the sanctions. They maintain Iran would make more concessions to get out of sanctions or could even eventually be brought down. Sanctions relief would give the Iranian government access to vast oil revenues it could use to destabilize the Mideast. Some Israeli officials suggest sabotage or even military strikes are preferable to keep Iran's nuclear program from advancing.

But that's seen as a risky approach that could lead to war. The Biden administration is looking to take Iran off the list of possible world flashpoints. And Iran wants to start doing business with the world. That might be enough to lead both countries to a new agreement, whether it's a return to the old deal or some half-step toward easing tensions. The latter could mean a partial deal — lifting some U.S. sanctions in exchange for Iran scaling back some of the steps it's taken.

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