Germany, France and the U.K. are ready to trigger a mechanism to reimpose United Nations sanctions on Iran, three European officials told CNN on Wednesday. Known as “snapback,” the mechanism is part of the 2015 Iran nuclear deal and could be activated as early as Thursday.

The process takes 30 days to go through, but that still leaves a window for diplomacy before the sanctions are reimposed. European leaders hope that will give Iran time to reengage in meaningful negotiations, open its facilities to international inspectors and take action to come back into compliance with its nuclear commitments.

Iran has threatened a strong reaction to the reimposition of sanctions, which could lead to more instability in the Middle East, where Iran and Israel have been at war for the past few weeks.

Snapback Trigger Nears Deadline

The snapback provision is part of the 2015 Joint Comprehensive Plan of Action, or JCPOA. If Iran fails to meet its obligations under the agreement, members have the ability to reimpose U.N. sanctions against the country. The ability to snapback sanctions expires in October.

Iran has significantly ramped up its nuclear program since former President Donald Trump unilaterally withdrew the U.S. from the JCPOA. The country is enriching uranium well above the limits set in the JCPOA, though it maintains that its nuclear program is peaceful. But inspectors and analysts have said that Iran’s progress is getting close to a point where they can start making weapons-grade material.

“It is not possible to return to the initial JCPOA. It’s almost impossible,” Rafael Grossi, the head of the International Atomic Energy Agency, or IAEA, said Wednesday.

Rubio said he coordinated with European allies this week ahead of Thursday’s deadline and said the snapback would provide “a very powerful piece of leverage on the Iranian regime.”

Inspection Teams Return

Iran’s parliament passed a law earlier this year to stop cooperating with international inspectors and the IAEA pulled its inspectors from the country in July, saying it could no longer verify Iran’s nuclear program amid the war.

But inspectors have started to return to Iran in recent days, including to the Bushehr nuclear power plant on Wednesday, according to Grossi. The head of the IAEA spoke in Washington on Wednesday.

“Today we are inspecting Bushehr. We are continuing the conversation so that we can go to all places, including the facilities that have been attacked,” he said.

Inspectors will only be able to access information the IAEA already has if they are not allowed back into certain facilities, Grossi said.

The IAEA’s ability to inspect comes from the Nuclear Non-Proliferation Treaty, or NPT, which Iran is a signatory of. The country reportedly is considering pulling out of the NPT if the U.N. reimposes sanctions.

Iranian Foreign Minister Abbas Araghchi said the inspectors were at Bushehr because of a Supreme National Security Council decision to allow them to monitor fuel replacement there. But he later denied that decision included a broader deal for “new cooperation.”

Impact of Recent Conflict

Iran and Israel have been engaged in a war in recent weeks. In June, Israel hit Iranian nuclear facilities, prompting Iran to retaliate with rocket attacks on Israeli cities. Iran’s forces were quickly overwhelmed and Israel launched missile attacks to stop them, which U.S. forces joined in the final days by striking three Iranian sites.

The IAEA withdrew its inspectors from Iran in July, citing the war as a reason that it would be impossible to monitor the nuclear sites. Satellite images in August showed blown-up entrances to Iran’s Isfahan Nuclear Technology Research Center, Reuters reported.

Tehran said that the IAEA was giving Israel a pretext to attack Iranian nuclear sites by reporting on non-compliance with safeguarding rules.

Iran Divided

Iran’s decision to allow the IAEA back into certain facilities has led to criticism at home. Parliamentary member Kamran Ghazanfari said Wednesday that Speaker Mohammad Bagher Ghalibaf’s comments in support of limited inspections had been an “explicit violation” of laws that parliament passed to suspend ties with the agency.

The decision to suspend ties with the IAEA was passed by parliament after the June conflict between Iran and Israel. The move was framed as necessary to counter foreign aggression and an IAEA that was biased against Iran.

European Diplomats Meet With Iran

European negotiators held talks with Iranian officials in Geneva on Tuesday. European officials said that they used the meeting as a last opportunity to try and prevent the reimposition of sanctions. It was not immediately clear if any progress had been made.

Ahead of the war, U.S. envoy Steve Witkoff was holding discussions to try and hammer out a new nuclear agreement. Those discussions collapsed as soon as the fighting began.

Grossi said Wednesday he was hopeful that the next 30 days could result in 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.