.

Germany, France and the United Kingdom are set to trigger the reimposition of United Nations sanctions on Iran, three European officials told CNN on Wednesday.

The so-called “snapback” mechanism is part of the 2015 Iran nuclear deal, and could be set in motion as early as Thursday.

The process will take 30 days to run its course, giving a small window for diplomacy. European leaders are hoping that Tehran will use that time to reenter serious negotiations, open up its facilities to international inspectors and take steps to comply with its nuclear obligations.

Iran has threatened harsh retaliation if sanctions return, and the move risks further unsettling a region already rocked by recent conflict.

The snapback provision is part of the 2015 Joint Comprehensive Plan of Action (JCPOA), which set limits on Iran’s nuclear program in exchange for the lifting of multilateral sanctions. Members can reinstate those UN sanctions if Iran is found in violation of the agreement. The authority for the move expires in October, prompting European action.

Iran has since ramped up its nuclear program far beyond JCPOA limits, after former President Donald Trump unilaterally withdrew the United States from the deal. Tehran maintains that its nuclear program is for peaceful purposes, but inspectors and analysts have warned that its capabilities are nearing weapons-grade territory.

“Going back to the original JCPOA would be almost impossible,” Rafael Grossi, the head of the International Atomic Energy Agency (IAEA), said Wednesday.

U.S. Secretary of State Marco Rubio, who coordinated with European counterparts this week, said that snapback “is a very powerful piece of leverage on the Iranian regime.”

Inspectors Are Back, Despite Harsh Climate

Iran’s parliament approved legislation to cut off cooperation with international inspectors this summer. Those measures came after the June conflict, when Israel struck Iran’s nuclear facilities, igniting a 12-day war. Iran retaliated with missile and drone attacks against Israeli cities, and U.S. forces participated in the final days, striking three Iranian sites.

Inspectors were pulled from Iran by the IAEA in July, with Grossi citing wartime conditions that made monitoring impossible. Satellite imagery later showed evidence of damage to entrances of Iran’s Isfahan Nuclear Technology Research Center.

Tehran has accused the agency of giving Israel a pretext for its attack by publicizing Iranian failures to live up to safeguard rules.

Iran Is Divided Over Allowing Inspectors Back

Iran has allowed IAEA inspectors back into some facilities, a move that drew criticism at home. Parliamentary member Kamran Ghazanfari accused Speaker Mohammad Bagher Ghalibaf of an “explicit violation” of laws suspending cooperation with the IAEA, after Ghalibaf was quoted as saying that inspections were allowed at some nuclear sites, and not at others.

Iran’s parliament had passed the law after the June conflict, in part as a defense against foreign aggression and what it deems IAEA bias in its reporting.

European negotiators met with Iranian representatives in Geneva on Tuesday in an eleventh-hour bid to avert sanctions. Sources indicated little progress in those talks.

In the weeks before the recent conflict, U.S. envoy Steve Witkoff had been involved in diplomacy to establish a new nuclear deal, but that process has been set aside with the eruption of fighting.

Grossi, who has met with Iranian officials over the course of the summer, remains hopeful that next month can produce a 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 mounting pressure from both the West and elements of its own political system. With the snapback mechanism set to expire in October, the coming weeks will be crucial in determining whether diplomacy survives, or whether sanctions and confrontation will define the next chapter of Iran’s nuclear story.