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Germany, France and the United Kingdom are set to trigger the return of United Nations sanctions on Iran, three European officials told CNN on Wednesday. The so-called “snapback” process could be initiated as early as Thursday, and takes 30 days to fully reimpose the sanctions that were suspended when the Iran nuclear deal went into effect in 2015.

European leaders are hoping that Tehran will use the window for diplomacy to recommit to good-faith negotiations, open its nuclear facilities to inspectors and reverse course on moves that have violated its obligations. But Iran has vowed retaliation if the sanctions are reimposed, and there is a real danger that renewed punitive measures could destabilize the region even further following months of conflict.

Under the Joint Comprehensive Plan of Action (JCPOA) agreed to in 2015, the snapback provision allows members to reinstate all UN sanctions on Iran if it’s in violation of the agreement. The mechanism to do so is set to expire in October, leaving the Europeans little time to act.

Iran has significantly ramped up its nuclear program since the United States withdrew from the JCPOA in 2018 under President Donald Trump, and gone far beyond the limits imposed on the number and enrichment level of its uranium stockpile. Tehran has long maintained that its program is entirely peaceful, but inspectors and outside analysts have expressed concern that it is coming into close contact with the quantity of material needed for a nuclear weapon.

“It is clear that if we go back to the original JCPOA, it will be almost impossible,” Rafael Grossi, head of the International Atomic Energy Agency (IAEA), said Wednesday.

U.S. Secretary of State Marco Rubio, who spoke with his European counterparts this week in preparation for the snapback, told reporters that the decision sends “a very powerful signal, which is a very powerful piece of leverage on the Iranian regime.”

Despite Iran’s parliament passing a law in June to cease cooperation with international inspectors, IAEA teams have recently returned to some of the country’s facilities. Grossi confirmed Wednesday that inspectors were at the Bushehr nuclear power plant.

“Today we are inspecting Bushehr,” he said during a news conference in Washington. “We are continuing the conversation so that we can go to all the places, including the facilities that have been attacked.”

The IAEA’s safeguards and inspections are part of the Nuclear Non-Proliferation Treaty (NPT) that Iran has signed but not withdrawn from. According to The New York Times, Iran has threatened to leave the NPT if the sanctions snapback is triggered.

Iranian Foreign Minister Abbas Araghchi said that IAEA inspectors were allowed to monitor the replacement of fuel at Bushehr “in line with a decision by the Supreme National Security Council,” but that there was “no new agreement for new cooperation between Iran and the IAEA.”

Fallout from Recent Conflict

Tensions with Iran have spiked since Israel targeted its nuclear facilities in June, which prompted a 12-day conflict. The exchange of attacks included Iranian missile strikes on Israeli cities, and U.S. forces joined the fray in the closing days to strike three Iranian sites.

The IAEA pulled its inspectors in July, and Grossi said it did so over the agency’s safety concerns as conditions were untenable in the midst of a war. Satellite imagery in August revealed blast damage to entrances at Iran’s Isfahan Nuclear Technology Research Center.

Iran later accused the agency of giving Israel “fuel and justification” to launch the attacks by publishing a report on Iran not being in compliance with safeguard rules and inspections.

Divisions Inside Iran

The decision to let the IAEA back into the Bushehr nuclear power plant has been criticized by lawmakers in Iran. Parliamentary member Kamran Ghazanfari said Wednesday that Speaker Mohammad Bagher Ghalibaf’s endorsement of the decision to allow “limited” inspections was an “explicit violation” of the parliament’s legislation passed in June after the conflict to suspend cooperation with the IAEA.

That legislation was part of Iran’s broad reaction to the Israel strike and what Tehran framed as Israeli aggression and bias in IAEA reports on its nuclear safeguards violations.

Diplomatic Window Narrowing

European negotiators met with Iranian counterparts in Geneva on Tuesday for final-ditch talks to avoid sanctions, but according to sources, little progress was made. Ahead of the June conflict, U.S. envoy Steve Witkoff was engaged in high-level talks on a new nuclear deal, which were suspended following the strikes.

Grossi said Wednesday that he’s cautiously optimistic that the next month could lead to de-escalation. “Don’t forget that there is still time, even if there is the triggering thing, there is a month, and many things could happen,” he said.

For now, Iran is facing both external pressure from the West and internal pressure in its own political system. With the snapback mechanism expiring in October, the next month could determine whether diplomacy has any life left in it—or whether sanctions and confrontation will further define the next chapter of Iran’s nuclear program.