An attempt by Iran to expand its nuclear programme has "no credible civil justification", leading European nations said.
The decision to begin enriching uranium to 20 per cent was a "serious negative development" that carried "very significant proliferation-related risks," the foreign ministers of the E3 countries Britain, Germany and France said.
It also throws into jeopardy the prospect of talks with US president-elect Joe Biden, they said.
The nations said the enrichment plan is in breach of the 2015 deal, known as the Joint Comprehensive Plan of Action, which Iran signed with six world powers to limit its nuclear capabilities.
The E3 said Iran’s action “risks compromising the important opportunity for a return to diplomacy with the incoming US Administration.”
“We strongly urge Iran to stop enriching uranium to up to 20 per cent without delay, reverse its enrichment programme to the limits agreed in the JCPOA and to refrain from any further escalatory steps which would further reduce the space for effective diplomacy,” it said.
“We remain in close contact with the other remaining JCPOA participants to assess how to best address Iran’s non-compliance within the framework [of the pact].”
The E3 has toiled to keep the JCPOA alive after outgoing US President Donald Trump withdrew the US from the deal in 2018. He also imposed sanctions on Iran. In 2019 Tehran breached limits set out in the agreement.