The E3 triggers snapback sanctions against Iran 2025

On 28 August 2025, the UK, Germany and France (collectively known as the ‘E3’) triggered a mechanism in the 2015 Iran nuclear agreement to introduce ‘snapback sanctions’ against Iran. The E3 said that Iran has been in a state of “significant non-performance” of the commitments it made under the deal.

When the E3 triggered the snapback mechanism, it started a 30-day countdown period. After the period elapses, all the UN sanctions against Iran that were lifted under the 2015 agreement will be reimposed. The reimposition can only be halted if the trigger is withdrawn or if a UN Security Council resolution is passed against it. The E3 have called on Iran to resume talks.

This research briefing explains the snapback mechanism and the sanctions to be reimposed, what the E3 have said, the Iranian and international response, and potential for talks to reach a new nuclear agreement.

What is the “snapback” mechanism?

Under the 2015 Iran nuclear agreement, a range of UN, EU and US sanctions were to be progressively lifted against Iran. These included lifting an arms embargo and restrictions on sensitive technology and goods.

“Snapback” restores all the UN sanctions against Iran lifted under the 2015 agreement unless a resolution is passed by the UN Security Council (UNSC) to continue with the agreement and its timetable. While the mechanism is not subject to a vote or veto at the UNSC, a resolution would be. The E3’s ability to trigger the snapback mechanism expires on 18 October 2025.

What did the E3 announce in August 2025?

In a letter to the UNSC in August 2025, the British, French and German foreign ministers said that Iran was in a state of “significant non-performance” with its commitments under the agreement. The ministers cited Iran’s enrichment of uranium beyond that required for civilian use, a lack of transparency in Iran’s stockpiles of uranium and heavy water, and a loss of access and knowledge of Iran’s nuclear sites by the International Atomic Energy Agency (IAEA), which is responsible for verifying Iran’s compliance.

The three countries formally triggered the snapback mechanism in the letter. The E3 said they were willing to extend the sanctions deadline if Iran agreed to resume negotiations, allowed the IAEA to resume its work, and addressed concerns about the extent and transparency of its nuclear programme. Iran has long said its nuclear programme is for civilian purposes only.

How have other states responded?

While the US welcomed the announcement and said it would be ready to engage in talks with Iran on a new agreement, Iran, China and Russia criticised the E3’s action and called it legally “flawed”. Russia argued that the E3 countries have broken the 2015 deal in retaining sanctions against Iran and that imposing snapback sanctions will “not create any international legal obligations”. The E3 say their right to use the mechanism is “unambiguous”.

China and Russia drafted a resolution for the UNSC which would extend the October deadline until April 2025. The resolution was rejected by a UNSC vote on 26 September 2025. South Korea, which then held the rotating UNSC presidency, also proposed a resolution to continue with the lifting of the sanctions process on 19 September. This was voted down. If no alternative resolution is passed by 27 September 2025, the snapback will come into force.

What other sanctions are imposed on Iran?

When the US withdrew from the 2015 Iran nuclear agreement in 2018, it reimposed all its sanctions on Iran and the Trump administration has continued its “maximum pressure” campaign of sanctions against Iran.

The UK and EU also continued their arms embargo and restrictions on missiles when these expired under the 2015 deal (in 2020 and 2023, respectively). However, despite continuing US sanctions, Iran’s oil trade with China (PDF), described by the US administration as a “lifeline” for Iran, remains high.