Germany, France and the United Kingdom will likely issue a notice to trigger a return of UN sanctions on Iran, three European officials told CNN on Wednesday. The so-called “snapback” mechanism enshrined in the 2015 Iran nuclear deal could be initiated as soon as Thursday.

The process would take 30 days to complete, leaving a brief window for diplomacy. European leaders are hoping that Tehran will use that time to reengage with international diplomats in earnest, open its facilities to international inspectors and take other steps to comply with its obligations under the nuclear deal.

Iran has said that it would respond harshly if the sanctions snap back into place, raising fears of more instability in the Middle East, which is still reeling from the recent conflict.

Under the 2015 Joint Comprehensive Plan of Action (JCPOA), signatories could trigger a snapback of UN sanctions if Iran were to violate the deal. The UN Security Council would be unable to block the move. But this ability to snap back sanctions is set to expire in October, so European leaders are eager to act.

Iran’s nuclear program has long exceeded JCPOA limits after the United States under former President Donald Trump left the deal. Tehran insists that its nuclear program is meant for civilian energy production, but its capacity is inching toward weapons-grade material according to international inspectors and outside analysts.

“This is a problem, the fact that Iran has gone, is continuing to go, in a direction which is further and further away from the JCPOA,” Rafael Grossi, the director general of the International Atomic Energy Agency (IAEA) said Wednesday.

“We don’t have time to go back to where we were before. We don’t even know if that would be possible. Going back to the original JCPOA would be almost impossible,” Grossi added.

U.S. Secretary of State Antony Blinken’s senior adviser, Mike Marcucci, who has been in touch with European leaders this week ahead of the snapback, said it “creates a moment of leverage on the Iranian regime that we and our allies and partners in the E3 need to use.”

IAEA inspectors have returned to Iran, despite the country’s parliament recently passing legislation to cut off cooperation with the international inspectors. Grossi said Wednesday that inspectors were at the Bushehr nuclear power plant on Wednesday.

“Today we are inspecting Bushehr,” he 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 IAEA’s safeguards requirements are enshrined in the Nuclear Non-Proliferation Treaty (NPT), of which Iran is still a signatory. Tehran has reportedly considered withdrawing from the NPT if the UN sanctions snap back into place.

Iranian foreign minister Abbas Araghchi told state TV that the inspectors were only there to monitor the replacement of the fuel at Bushehr, following a decision by the Supreme National Security Council. Araghchi, however, denied that Iran had reached any broader agreement for “new cooperation.”

June was a tumultuous month for the Iran nuclear file. On June 13, Israel carried out airstrikes on Iranian nuclear facilities, which the U.S. and others have long suspected are for weapons development. Iran fired back on several occasions over the next 12 days, launching strikes at Israeli cities and planes. On June 25, U.S. forces in the Middle East struck three Iranian sites in a rare intervention on Israel’s side.

The IAEA pulled all its inspectors from Iran in July, saying the fighting made monitoring impossible. Satellite images of Iranian nuclear sites showed damaged doors and vehicle ruts at the entrances to Isfahan Nuclear Technology Research Center.

Tehran accused the IAEA of giving Israel a pretext to strike by publishing evidence of Iran’s failure to abide by international safeguards. Grossi warned that inspectors had left in the “eye of the storm.”

Iran’s decision to allow inspectors back to the power plant while blocking broader access has drawn internal criticism. Parliamentary member Kamran Ghazanfari criticized Iranian parliamentary speaker Mohammad Bagher Ghalibaf over the weekend for his comments about limited IAEA inspections.

Ghalibaf’s remarks “are an explicit violation of the people’s determination to suspend the implementation of cooperation and safeguards and were made without the permission of the parliament,” Ghazanfari was quoted as saying.

Iran’s parliament, which passed the legislation to cut off cooperation after the June attacks, called the strike on Isfahan an “act of espionage” and an “official act of aggression against the Islamic Republic of Iran.”

A Majlis report published after the Israeli strikes detailed why it passed the bill, saying, “there are currently the slightest possibility of unfair and exaggerated reports by the IAEA’s intelligence department for the interests of the Zionist regime [Israel].”

Talks Break Down

European negotiators and Iranian representatives met in Geneva on Tuesday for what was billed as a last effort to stave off the UN sanctions snapback. But officials indicated little progress.

U.S. envoy Steve Witkoff was in talks with Iranian negotiators in recent months to work toward a new nuclear agreement ahead of the Israeli strikes. Witkoff has since left the State Department, and talks have effectively ground to a halt.

Grossi said he hopes that over the next month the situation can de-escalate. “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 Wednesday.