Germany, France and the United Kingdom are set to trigger the reimposition of UN sanctions on Iran, three European officials said on Wednesday. The so-called “snapback” provision of the 2015 nuclear deal with Tehran could be activated as early as Thursday, CNN reported.

It would take 30 days for the sanctions to be fully reimposed, providing a window for diplomacy. European leaders are pinning hopes that Tehran will use that time to return to meaningful negotiations, open up its nuclear facilities to inspectors and begin to take concrete steps towards compliance.

Iran has threatened retaliation if sanctions are reimposed, raising the risk of further regional instability after recent conflict.

Snapback Mechanism Nears Expiration

The snapback provision of the Joint Comprehensive Plan of Action (JCPOA) allows members to reinstate UN sanctions if Iran is deemed to be in violation. European leaders say Iran is in breach of the 2015 agreement. The authority to reinstate sanctions will expire in October.

Iran has since the US exit from the agreement under Donald Trump “accumulated equipment and enriched uranium far in excess of JCPOA limits,” as per a recent report in Foreign Policy. Tehran has built up its uranium enrichment capability and reduced the frequency of inspections by International Atomic Energy Agency (IAEA) inspectors. The enriched uranium stockpile is now “only a chemical, physical barriers away from weapons-grade material,” Grossi warned.

“Going back to the original JCPOA would be almost impossible,” the head of IAEA Rafael Grossi said on Wednesday.

“We have this additional possibility of triggering what’s called the snapback,” US Secretary of State Marco Rubio, who spoke with his European counterparts this week, said. “It’s a very powerful piece of leverage on the Iranian regime,” Rubio said of the snapback mechanism.

Inspectors Return Amid Tense Climate

IAEA inspectors returned to Iran after its parliament passed legislation ordering the end of all cooperation with international inspectors. Grossi confirmed that the agency’s team is now at the Bushehr nuclear power plant.

“Today we are inspecting Bushehr. It’s the third day of inspections, of course, in different parts of the country,” Grossi told reporters in Washington, according to Reuters. “We are continuing the conversation so that we can go to all places, including the facilities that have been attacked.”

IAEA safeguards and inspection regimes are based on the Nuclear Non-Proliferation Treaty (NPT), of which Iran is still a signatory. But Iran is reportedly also considering withdrawal from the NPT if sanctions are reimposed.

Iranian Foreign Minister Abbas Araghchi said the IAEA was able to monitor fuel replacement at Bushehr only after Supreme National Security Council decided to do so. He denied that it was part of a broader agreement with the IAEA over “new cooperation.”

Fallout from Recent Conflict

Tensions have soared in the past weeks since Israeli strikes on Iran’s nuclear facilities in June. The Israeli strikes began a 12-day conflict in which Iran attacked Israeli cities in retaliation. In the final days, US forces joined the fray, striking three Iranian sites.

IAEA inspectors withdrew its team from Iran in July, saying it was unsafe to operate during wartime. Satellite imagery since then has revealed that entrances to Iran’s Isfahan Nuclear Technology Research Center appear to have been damaged, likely during Israeli strikes.

Tehran has accused the IAEA of in effect giving Israel a pretext to attack by releasing information that shows Iran was in violation of safeguards rules.

Divisions Inside Iran

Tehran’s decision to allow IAEA inspectors into certain nuclear facilities has already drawn criticism at home. Parliamentary member Kamran Ghazanfari lambasted speaker Mohammad Bagher Ghalibaf’s remarks suggesting limited cooperation with IAEA. Ghazanfari tweeted the speaker was making “explicit violation” of the legislation parliament had passed in July.

Parliament had passed legislation after the June conflict to halt cooperation with the IAEA. The measure was justified as a means of protection from foreign aggression and the agency’s “duplicitous and politicized reports.”

Diplomatic Window Narrowing

European negotiators met with Iranian representatives in Geneva on Tuesday, in an attempt to head off sanctions. But sources told CNN little headway was made in the meeting.

Diplomacy had been ongoing, even ahead of the Israel-Iran conflict, as US envoy Steve Witkoff attempted to work with Iran to negotiate a new nuclear deal. That process came to a halt with the outbreak of the conflict.

Grossi remains hopeful that Iran may use the next month to de-escalate. “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 under pressure from the West, and even from within its own system. The snapback mechanism is set to expire in October, meaning the next month will determine whether diplomacy has a future in Iran’s nuclear story.