Germany, France and the United Kingdom are expected to activate a process to reimpose United Nations sanctions on Iran, three European officials told CNN on Wednesday. Known as a “snapback,” the provision, part of the 2015 Iran nuclear deal, could be triggered as early as Thursday, the officials said.

The 30-day process that must unfold before the sanctions are back in place leaves little time for further diplomacy. European leaders hope the next month will be enough time to prod Iran into returning to serious talks, opening its nuclear facilities to international inspectors and taking steps to come back into compliance with its obligations.

Iran has signaled it will respond harshly to a return of the sanctions, however, increasing the risk of further turbulence in a region already roiled by fighting earlier this summer.

Snapback provision looming

The provision for snapback is part of the 2015 Joint Comprehensive Plan of Action (JCPOA), which allows members to reinstate UN sanctions in the event of Iran’s non-compliance with the deal. The authority to activate the mechanism is set to expire in October.

Iran has accelerated its nuclear program since the United States left the agreement under former President Donald Trump. The program has since grown far beyond the limits outlined in the JCPOA. Iran has said the program is for peaceful purposes only, but inspectors and analysts say Tehran’s nuclear program is 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.

U.S. Secretary of State Marco Rubio, who met with European counterparts this week to coordinate action on Iran, called snapback “a very powerful piece of leverage on the Iranian regime.”

IAEA inspectors teams were expected back at Iranian nuclear facilities as early as last week, despite the Iranian parliament having passed legislation ordering an end to all cooperation with international inspectors.

On Wednesday, Grossi confirmed inspectors were on the ground at the Bushehr nuclear power plant. “Today we are inspecting Bushehr,” he said Wednesday to reporters in Washington. “We are continuing the conversation so that we can go to all places, including the facilities that have been attacked.”

The IAEA’s inspections are part of the safeguards under the Nuclear Non-Proliferation Treaty (NPT). Iran is still a signatory to the treaty and as such would have to leave the NPT before it would no longer have to cooperate with IAEA inspectors, Grossi said. He said one of the options under consideration by Tehran in the event of a snapback was to leave the NPT.

Iranian Foreign Minister Abbas Araghchi said the IAEA team was at Bushehr monitoring fuel being replaced at the facility following a decision by the Supreme National Security Council. He said the team did not have the same powers as IAEA inspectors that would have been at the plant previously. He denied there was an agreement for “new cooperation.”

Tensions have been building since Israeli forces targeted Iran’s nuclear facilities in June, setting off a 12-day conflict in the region. Iranian retaliatory attacks targeted Israeli cities, and U.S. forces launched strikes against Iranian targets in the final days of the conflict. The U.S. said the strikes were in retaliation for Iranian attacks on American bases in Iraq and hit three Iranian sites.

The IAEA pulled out its inspectors in July, saying it was not safe for them to be on the ground in the middle of a war. Satellite images later showed holes at the entrance to the Isfahan Nuclear Technology Research Center, which was hit during the conflict.

Iran accused the IAEA of essentially giving Israel a pretext to strike by reporting Iranian non-compliance with IAEA safeguard rules.

Iran divisions over nuclear inspectors

The decision by Iran to allow IAEA inspectors into some facilities has met with opposition inside Iran. Kamran Ghazanfari, a member of the Iranian parliament, slammed comments by Speaker Mohammad Bagher Ghalibaf in support of allowing “conditional, limited” inspections at some facilities.

The legislation to end cooperation with the IAEA was passed by parliament in the aftermath of the June conflict, as Tehran claimed it needed to defend against foreign aggression and biased reporting by the IAEA.

Diplomatic window closes on Iran

European negotiators met with Iranian officials in Geneva on Tuesday in an attempt to avoid snapback. However, sources with knowledge of the meeting said there had been no breakthrough in the talks.

Rubio said the possibility of a new nuclear deal with Iran was “effectively over” after talks headed by U.S. envoy Steve Witkoff collapsed with the outbreak of fighting this summer.

Grossi said he was optimistic the next month could see tensions 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 finds itself facing pressure from the West and the threat of snapback, as well as criticism from its own parliament. With the end of the snapback mechanism looming, the next month or so may decide whether diplomacy remains a path forward—or whether sanctions and confrontation will dominate the next chapter of Iran’s nuclear story.