Germany, France and the United Kingdom are expected to trigger the reimposition of United Nations sanctions on Iran, three European officials told CNN on Wednesday. The so-called “snapback” mechanism enshrined in the 2015 Iran nuclear deal, could be set in motion as soon as Thursday.

The process takes 30 days to complete, leaving a small window for diplomacy. European leaders hope Iran will use that time to reengage in serious negotiations, open its facilities to international inspectors and take steps to comply with its nuclear obligations.

Iran has threatened drastic retaliation if sanctions are reimposed. This raises the specter of more chaos in a region already roiled by a conflict just weeks ago.

Members of the 2015 Joint Comprehensive Plan of Action (JCPOA) signed in Vienna agreed to allow the snapback provision to restore UN sanctions should Iran violate the deal. That authority is set to expire in October.

Iran has accelerated its nuclear program far beyond the limits established in the JCPOA. Tehran moved to exceed those limits after former President Donald Trump pulled the U.S. out of the deal.

Iranian officials have consistently said the program is peaceful. But inspectors have said Iran’s stockpile and enrichment levels are reaching the point where they could be used to make weapons. On Wednesday Rafael Grossi, head of the International Atomic Energy Agency, said it could be “almost impossible” to go back to the original JCPOA.

U.S. Secretary of State Marco Rubio spoke to his European counterparts this week to coordinate messaging on the issue. He said Wednesday the snapback is “a very powerful piece of leverage on the Iranian regime.”

Inspectors Return to War-Zone

Iranian lawmakers approved legislation last month to end cooperation with international nuclear inspectors. The IAEA confirmed its inspectors had been at the Bushehr nuclear power plant on Wednesday.

“Today we are inspecting Bushehr,” Grossi told reporters in Washington. “We are continuing the conversation so that we can go to all places, including the facilities that have been attacked.”

The agency’s safeguards are not an issue of Iran’s voluntary cooperation with the IAEA but are enshrined in the Nuclear Non-Proliferation Treaty (NPT). Iran remains a signatory to the NPT, but is reportedly considering withdrawing if sanctions are reimposed.

Iranian Foreign Minister Abbas Araghchi said the inspectors were only at the site to monitor fuel being replaced. They were able to do so based on a decision from the Supreme National Security Council, he said. Araghchi denied there had been any new agreement on cooperation, calling the claim “not true.”

Fallout from Recent War

Israel bombed Iran’s nuclear facilities in June, setting off a 12-day conflict. Iran fired missiles at Israeli cities in retaliation, with U.S. forces intervening in the final days. American aircraft struck three Iranian sites.

The IAEA said in July it was forced to withdraw its inspectors because the war made inspections impossible. Satellite images have since shown entrances to Iran’s Isfahan Nuclear Technology Research Center appeared to have been damaged.

Tehran said it accused the IAEA of helping Israel justify its strike by publicizing information Iran had violated safeguard rules.

Opposition Inside Iran

Allowing IAEA inspectors to return to some facilities has been met with criticism inside Iran’s parliament. Kamran Ghazanfari, a parliamentary member, lambasted Speaker Mohammad Bagher Ghalibaf for comments that appeared to suggest limited cooperation was on the table.

“Iranian Armed Forces, as well as speaker’s words on the inspection of some Iranian nuclear sites by IAEA, and entering into negotiations and making concessions, are an explicit violation of laws related to suspending cooperation with the AIEA,” he said in a statement Wednesday.

Iran’s parliament approved the legislation to end cooperation with inspectors after the June conflict. It described the measure as a “necessary” move to counter foreign aggression and the IAEA’s “biased and unbalanced reporting.”

Iran Tried to Delay Diplomacy

European negotiators met with Iranian officials in Geneva on Tuesday to discuss a last-minute effort to prevent snapback. There was little indication of any progress during those discussions, per sources.

In the weeks leading up to the conflict, U.S. special envoy Steve Witkoff had been meeting with Iranian officials in Europe to try to negotiate a new deal on Iran’s nuclear program. The talks ended once the fighting broke out.

Grossi said he is “hoping with all my heart” that the next month could bring some kind of 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.

But for now Iran faces increased pressure from both the West and domestic critics. With the snapback mechanism set to expire in October, the coming weeks may determine whether diplomacy can survive—or whether sanctions and confrontation become the defining feature of Iran’s next chapter.