President Joe Biden’s team is beginning to grapple with the possibility that the 2015 nuclear accord with Iran he promised to revive may soon be beyond saving.

Hopes for a quick reentry to the accord that Donald Trump abandoned have dimmed after six rounds of negotiations in Vienna with little sign of when a seventh might start. The stalemate is compounded by Iran’s technological advances and the election of a new hard-line president, raising doubt about whether the agreement reached in 2015 would be sufficient to constrain the country’s nuclear ambitions anymore.

This week provided another example of just how far Iran has advanced in the three years since then-President Trump renounced the Joint Comprehensive Plan of Action in 2018 and began his “maximum pressure” campaign with its array of sanctions. On Tuesday, the International Atomic Energy Agency reported that Iran has taken steps to make metal fuel plates with uranium it has enriched to 20% purity. That’s banned by its deal with world powers and marks a significant step toward production of a nuclear bomb.

The more knowledge Iran gains, “the more difficult it becomes to ensure that the JCPOA can be the same bulwark against nuclear weapons development as it was in 2015,” said Kelsey Davenport, director for nonproliferation at the Arms Control Association. “It’s a dangerous game. Iran is putting the Vienna talks at risk by pursuing nuclear activities that cannot be fully reversed.”

The election of Ebrahim Raisi as president in June also makes it more difficult: A key strategy for the U.S. has been to rejoin the accord and then reach what it calls a “longer and stronger” deal addressing issues such as extending restrictions on Iran’s nuclear program, some of which are set to expire as soon as 2025. The U.S. also would seek to open negotiations to limit Iran’s ballistic missile program and its support for groups the U.S. considers terrorists.

Raisi has made clear that his government, which will take office in August, will entertain no such discussions.

“That illusion is gone now,” said Richard Goldberg, an analyst at the Foundation for Defense of Democracies, which opposes the nuclear accord. “It’s been taken away by Raisi.”

Iran would receive some clear benefits from finding a way to get back into the JCPOA with the U.S.: the end of many punishing sanctions that hobbled its economy, before and during the COVID-19 pandemic. The harshest restriction was the effective ban on the legal sale of oil abroad, once Tehran’s biggest source of external revenue.

But three years in, Iran’s government has managed to weather those sanctions, as well as other crises such as its own military’s downing of a passenger plane following the U.S. killing of a top general early last year.

Hovering over the efforts to revive the old deal is a fundamental question: A central goal of the 2015 agreement was to constrain Iran’s nuclear program tightly enough that it would need a full year to build a bomb if it chose to “break out” of the accord. But if Iran already has gained the ability to produce a bomb in a few months, and eventually a few weeks, is there any point in trying to get back into the deal?

Even as Iranian leaders insist they have no intention of building a bomb, they have booted out many international inspectors and are developing centrifuges that can enrich uranium 50 times faster than previously. Its nuclear “breakout” time has shrunk to “perhaps a few months,” according to State Department spokesman Ned Price.

“We are conscious that as time proceeds Iran’s nuclear advances will have a bearing on the view of returning to the JCPOA,” Price told reporters at a briefing on Tuesday. “One of the chief advantages of the JCPOA was the elongation of that breakout time. If those advantages start to disappear, we’ll have to reassess where we are in this process.”

That’s forced some creative thinking, according to one person familiar with the matter. One idea is to require Iran to store its most advanced centrifuges under IAEA seal until the accord permits them to be used in 2025 under the deal’s “sunset” provisions.

Another idea is for Iran to reduce the number of centrifuges it has. People familiar with the matter say those technical talks have gone on while the broader negotiations take place.

But skeptics of the deal — including Republicans and some Democrats in Congress — have long argued that the accord at best simply delayed Iran’s nuclear program.

“Much has unfolded since the 2015 Iran nuclear deal,” said Sen. Ben Cardin, D-Md. “The world is a different place.”

Now, denying Iran the technology to build a bomb may be a lost cause.

“That ship has sailed — Iran today is in possession of nuclear weapons-grade material and advanced centrifuges” said Ray Takeyh, senior fellow at the Council on Foreign Relations. “Anybody who thinks that getting back to the JCPOA puts Iran’s nuclear program back in a box has no precise understanding of the box.”

There’s also the knowledge on both sides that any accord reached now could be fleeting anyhow. If a Republican wins the White House in 2024, a revived deal would probably be scrapped again. That’s resulted in short-term thinking on both sides, trying to extract gains now and leave the future to resolve itself later.

For now, though, there simply may be no other choice. Biden administration officials remain determined not to adhere to the Trump approach of provocation heaped on provocation. They are looking for some way to ease the tension and get back into a nonproliferation deal.

And they still argue that, for all its flaws, the JCPOA remains powerful. According to one person familiar with the U.S. team’s negotiating stance, returning to the deal would have nonproliferation benefits — at least for the time being.

“The approach reconstituting what we had and then trying to make as much progress after that is the right way to proceed — I really don’t see any other alternative,” said Suzanne DiMaggio, a senior fellow at the Carnegie Endowment for International Peace. “It’s important to look at the JCPOA not only as a sound nonproliferation agreement but also as a mechanism for deescalation.”