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Three European officials told CNN on Wednesday that Germany, France and the United Kingdom are poised to set off a process that would reimpose United Nations sanctions on Iran. The so-called “snapback” mechanism could be activated as soon as Thursday.

It takes 30 days for the process to work through the United Nations, giving Iran a brief window to negotiate, the officials said. But time is of the essence, with the ability to snap back sanctions set to expire in October.

The European powers hope Iran will use the time to return to the negotiating table and make progress on key issues: opening up its facilities to international inspectors and showing it is abiding by its nuclear commitments. Iran has signaled it could try to retaliate if sanctions are brought back, and that could mean more turmoil for a region still reeling from the war earlier this summer.

A looming window

In the 2015 Joint Comprehensive Plan of Action (JCPOA) nuclear deal with Iran, member states can invoke a “snapback” to reinstate UN sanctions. The provision allows any member that was part of the original JCPOA to restore UN sanctions if Iran is not in compliance with the agreement.

Iran has ramped up its nuclear program far beyond JCPOA limitations since former President Donald Trump left the deal, though the Iranian government has maintained that it is intended for peaceful purposes. But Iran’s growing capabilities are edging closer to a point where the nuclear material could be used for weapons, as per the treaty.

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

The US secretary of state, Marco Rubio, said snapback is “a very powerful piece of leverage on the Iranian regime.” He said in a statement to CNN. The European trio spoke with their US counterpart this week to coordinate their next steps.

Inspectors are back

Iran’s parliament approved a bill in late July that ordered a halt to all cooperation with international nuclear inspectors, including IAEA teams. But teams returned to some Iranian facilities in recent days, Grossi said.

“Iran and the IAEA have confirmed that inspectors are now at Bushehr,” Grossi told a briefing in Washington. “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.”

The IAEA’s inspections of Iran are part of the NPT, a treaty that Iran has not left. One of the options Tehran has said it will consider if sanctions return is to quit the NPT.

The IAEA was at the Bushehr nuclear power plant to monitor fuel replacement “following the decision of the Supreme National Security Council of the Islamic Republic of Iran,” Iran’s foreign minister, Abbas Araghchi, said at a news conference Wednesday.

But Araghchi said Tehran and the IAEA did not reach an agreement for “new cooperation.” The IAEA chief had asked Iran to allow more access to its sites.

Snapback clouds

Tensions have been high between the two countries since Israel hit Iran’s nuclear facilities in early June. The 12-day conflict saw Iranian missiles fire on Israeli cities, which the US forces eventually joined to strike Iranian military sites in the war’s final days.

The IAEA withdrew its inspectors in July, when the war broke out, and monitoring activities were impossible. It later reported seeing damage at entrances to Iran’s Isfahan Nuclear Technology Research Center in satellite imagery.

Tehran accused the IAEA of effectively giving Israel the green light to bomb Iranian nuclear sites by leaking information about Iran’s compliance with safeguard rules to Israel.

Political pressure

Allowing IAEA inspectors back into some Iranian nuclear facilities has attracted criticism at home. Kamran Ghazanfari, a member of Iran’s parliament, said speaker Mohammad Bagher Ghalibaf’s comments that Iran may allow inspectors in some facilities is an “explicit violation” of laws passed in July and August suspending all cooperation with the IAEA.

Parliamentarians passed the bill following the June war. At the time, it was sold as a bulwark against foreign aggression and the politicization of IAEA reports.

Wednesday’s talks

European negotiators met with Iranian counterparts in Geneva on Tuesday in a bid to prevent snapback sanctions. However, according to two sources, little headway was made.

US diplomat Steve Witkoff had been working in Geneva ahead of the June conflict on a new nuclear agreement between Iran and the US, and European nations are now in talks on behalf of the US. Those talks had ended with the start of the war.

IAEA’s Grossi sounded a note of hope Wednesday. “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.

As of now, Iran is under pressure at home and abroad. With the European powers’ ability to trigger snapback sanctions set to expire in October, the coming month may well determine whether diplomacy remains an option—or whether escalation takes over in the next chapter of Iran’s nuclear program.