The U.N. nuclear watchdog, the IAEA, and Tehran said on Wednesday that Iran had started the work, the latest breach of its agreement with six major powers as it presses for a lifting of U.S. sanctions.

“We strongly encourage Iran to end this activity, and return to full compliance with its commitments under the Joint Comprehensive Plan of Action without delay, if it is serious about preserving this agreement,” France, Britain and Germany said in a joint statement.

Iran has been accelerating its breaches in the past two months. Some of those steps were triggered by a law passed in response to the killing of its top nuclear scientist in November, which Tehran has blamed on its arch-foe Israel.

They are also part of a process of retaliation that Tehran started in 2019 in response to U.S. President Donald Trump’s withdrawal from the deal and reimposition of sanctions that the United States had scrapped in exchange for restrictions on Iran’s nuclear activities.

The three powers, who remain in the deal with China and Russia, said they were “deeply concerned”, and that Iran’s production of uranium metal had no civilian credibility but potentially serious military implications.

Iran’s Atomic Energy Organization said the decision to produce the fuel was unrelated to recent breaches.

Read More: Reuters