Germany, France and the United Kingdom are set to trigger the reimposition of UN sanctions on Iran, three European officials told CNN on Wednesday. Known as the “snapback” mechanism, the move could happen as early as Thursday, the officials said.

The move takes 30 days to process, leaving limited time for diplomacy. European officials hope Tehran will use that time to get back to the negotiating table, allow inspectors into its facilities, and reverse some of its noncompliance with its nuclear obligations.

Iran has threatened retaliation if sanctions are reimposed, a prospect that could further destabilize the Middle East, where recent fighting has already upended the region.

Deadline Looming for ‘Snapback’

Negotiated in 2015, the Joint Comprehensive Plan of Action, known as the JCPOA, included the snapback mechanism, which allows members of the accord to reestablish UN sanctions on Iran if the country fails to comply with the deal. The provision is set to expire in October.

Iran has ramped up its nuclear program well beyond the parameters set by the JCPOA since former President Donald Trump unilaterally withdrew from the agreement. Iran has long maintained its nuclear program is for peaceful purposes, but its facilities are approaching levels that could be used for weapons development, experts and inspectors have said.

“There’s no turning back to the original JCPOA, that would be almost impossible,” Rafael Grossi, the head of the United Nations International Atomic Energy Agency, said Wednesday.

US Secretary of State Marco Rubio, who spoke to European allies this week in preparation for the snapback, called the action “a very powerful piece of leverage on the Iranian regime.”

Iran’s parliament passed legislation earlier this month to cut off cooperation with international inspectors. On Wednesday, Grossi confirmed IAEA teams were present at the Bushehr nuclear power plant.

“Today we are inspecting Bushehr, and we have been given access and the ability to go where we need to go,” he said 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 safeguards are based in the Nuclear Non-Proliferation Treaty, or NPT, which Iran has not pulled out of. One of the options Iran could take if sanctions are reimposed is withdrawing from the NPT, according to people familiar with Iranian discussions.

Iranian foreign minister Abbas Araghchi said the IAEA inspectors were allowed to observe the Bushehr facility to make sure no further proliferation would result from the fuel rod replacements.

“We don’t have a new agreement on new cooperation,” Araghchi added at a news conference.

Tensions boiled over in June, when Israel reportedly struck Iran’s nuclear facilities, setting off a 12-day conflict. Iran retaliated with attacks on Israeli cities, and in the final days, US forces also struck three Iranian sites.

The IAEA pulled out its inspectors in July, saying the conditions of war made it impossible to continue monitoring Iranian activities. Satellite photos later showed damage to entrances of Iran’s Isfahan Nuclear Technology Research Center.

Iran had accused the agency of giving Israel an excuse to launch its strikes by releasing information that showed the country was not in compliance with some safeguard rules.

Iranian Parliamentary Disagreement

Iran’s decision to allow IAEA inspectors back into certain facilities has not been met without criticism at home. Parliamentary member Kamran Ghazanfari said Speaker Mohammad Bagher Ghalibaf’s statements that it was possible to allow limited inspections by the agency was an “explicit violation” of legislation that had been passed in the body’s session on suspending the cooperation with the IAEA.

The legislation was passed in the wake of the June conflict. At the time, Tehran argued that the move was necessary to defend itself against foreign aggression and the IAEA’s “bias” in its reports.

European diplomats were in Geneva on Tuesday for a last-minute meeting with Iran, but both sides suggested little was accomplished. Before the June conflict, US envoy Steve Witkoff was active in negotiating with Iran, working to develop a new nuclear deal.

Talks effectively ended with the onset of fighting, but the window for diplomacy is still open. Grossi said he was hopeful that the coming month might see a de-escalation in tensions.

“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.