Germany, France and the United Kingdom are “very likely” to trigger a mechanism reimposing United Nations sanctions on Iran, three European officials told CNN on Wednesday. The so-called “snapback” mechanism would likely be set in motion as soon as Thursday.

The 30-day process gives little time for diplomacy, as European leaders hope Tehran will use the interim to reengage in serious negotiations, open its facilities to international inspectors, and show signs of complying with its nuclear obligations. But Iran has threatened extreme retaliation if sanctions are renewed, and the risk of further instability in the Middle East, already roiled by recent conflict, is high.

Snapback Process Nears Deadline Officials in Germany, France, and the UK are united in their desire to see the UN snapback process initiated, CNN reported. According to the 2015 Iran nuclear deal, known as the Joint Comprehensive Plan of Action (JCPOA), the snapback provision allows JCPOA members to restore UN sanctions on Iran in the event of Iranian non-compliance with the agreement.

The authority to trigger snapback will expire in October. Iran’s nuclear program has advanced to levels far beyond JCPOA limits since the United States left the agreement under former President Donald Trump. Iran continues to maintain its nuclear program is for peaceful purposes, but inspectors and analysts say its nuclear capabilities are now nearing weapons-grade levels.

“Going back to the original JCPOA would be almost impossible,” Rafael Grossi, head of the International Atomic Energy Agency (IAEA), said Wednesday. “We were dealing with JCPOA-plus measures that were taken by Iran. I don’t think this situation will be reversible,” added a European diplomat. European foreign ministers are discussing the “snapback” with their Iranian counterparts and with U.S. Secretary of State Marco Rubio this week.

Rubio, speaking to reporters Wednesday, described the snapback as “a very powerful piece of leverage on the Iranian regime.” Inspectors Return Despite Threats Iran’s parliament approved legislation in July to stop cooperating with international inspectors over alleged bias in IAEA reporting. But IAEA inspectors returned to the Islamic Republic in recent days, as the European Union began its snapback process, after a disputed high-level meeting with Iranian leaders last week. Grossi confirmed to reporters on Wednesday that IAEA inspectors were in Bushehr, the location of a nuclear power plant, at the time of his interview.

“Today we are inspecting Bushehr,” he said. “We are continuing the conversation so that we can go to all places, including the facilities that have been attacked.” The IAEA’s safeguards stem from the Nuclear Non-Proliferation Treaty (NPT), of which Iran is a signatory. The IAEA has said it would leave Iran if it were to withdraw from the NPT, which is reportedly among the options Tehran is weighing in the event that sanctions are reimposed. Iran’s Foreign Minister Abbas Araghchi acknowledged the IAEA was monitoring fuel replacement at the Bushehr plant on Wednesday following a decision by the Supreme National Security Council. But he rejected any wider agreement on “new cooperation” with the agency.

Fallout from Recent Conflict Tensions between Iran and Israel have been high following strikes on Iran’s nuclear facilities in June. The attack began a 12-day war between Iran and Israel, with Iranian retaliatory attacks on Israeli cities and U.S. forces getting involved in the final days to strike three Iranian sites. The IAEA pulled its inspectors in July, saying it was no longer possible for them to work during wartime conditions.

Satellite images have since shown that entrances at Iran’s Isfahan Nuclear Technology Research Center were destroyed during the June strikes. Tehran has accused the IAEA of essentially giving Israel a “Green Light” for its strikes by publicizing Iran’s non-compliance with safeguard rules. Divisions Inside Iran The move to let IAEA inspectors in some facilities has been met with criticism from the Iranian government.

Parliamentary member Kamran Ghazanfari on Wednesday called out Speaker Mohammad Bagher Ghalibaf’s supportive remarks on limited inspections as “an explicit violation of Iran’s parliament law on suspending cooperation with the AIEA.” The parliament legislation to stop cooperating with international inspectors was passed after the June conflict. The move was framed as necessary to protect Iran against foreign aggressions and what was portrayed as biased IAEA reporting.

Diplomatic Window Shrinks Negotiators for the European Union met with Iranian officials in Geneva on Tuesday in a last-minute bid to stave off snapback. But European officials said little progress was made. U.S. envoy Steve Witkoff had been meeting with Iranian officials in Geneva ahead of the Israeli strike on Iran’s nuclear facilities to work toward a new nuclear agreement. Those efforts came to a halt when the fighting began.

Grossi on Wednesday said he was still hopeful that Iran could be de-escalated over the next month. “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. In the meantime, Iran’s nuclear program continues to advance to levels well beyond those allowed in the original JCPOA, and with little time remaining on the authority to trigger UN snapback, the coming weeks could determine whether diplomacy or sanctions and confrontation will be the next chapter of Iran’s nuclear saga.