Britain, France and Germany called on Donald Trump on Thursday to uphold a pact curbing Iran’s nuclear ambitions on the eve of a sanctions ruling by the U.S. president they fear could torpedo an accord he has relentlessly criticized. 

Hailed by its admirers as key to stopping Iran from building a nuclear bomb, the deal lifted economic sanctions in exchange for Tehran limiting its nuclear program. It was also signed by China, France, Russia, Britain, Germany and the European Union. 

In sharp contrast to Trump’s view that the 2015 pact was “the worst deal ever negotiated”, the foreign ministers of the three countries and the EU’s top diplomat said there was no alternative to it and that sanctions should remain lifted.

“We agree on this approach, we want to protect (the deal) against every possible decision that might undermine it,” Germany’s Sigmar Gabriel said alongside his French and British counterparts and EU foreign policy chief Federica Mogherini after meeting Iran’s Foreign Minister Mohammad Javad Zarif.

“It is absolutely necessary to have this to prevent the development of nuclear weapons at a time when other parts of the world are discussing how to get them,” Gabriel said, later specifically mentioning North Korea in his remarks.

Trump’s choice comes at a delicate time for Iran’s government, which faced protests over economic hardships and corruption that are linked to frustration among younger Iranians who hoped to see more benefits from the lifting of sanctions.

“The deal is working. It is delivering on its main goal which means keeping the Iranian nuclear program in check and under close surveillance,” Mogherini said, adding that the International Atomic Energy Agency had shown in nine reports that Iran is meeting its commitments.

British Foreign Secretary Boris Johnson said the pact was also a way for Iran to show it was “a good neighbour” in the region by complying.