The foreign ministers of Germany, France and Britain on Wednesday jointly pressed Iran to reverse its decision to start enriching uranium to levels beyond the limits of a 2015 nuclear agreement.

From Monday, Iran started enriching uranium to levels unseen since the landmark deal, having informed the International Atomic Energy Agency last week of its plans to increase enrichment to 20%.

The development at Iran's underground Fordo facility puts Tehran a technical step away from making weapons-grade levels of 90%.

The three European countries said the "serious negative development" undermines assurances made by parties to the 2015 Joint Comprehensive Plan of Action (JCPoA) on December 21. In a statement, the three acknowledged their desire to uphold the deal and hailed the prospects of a US return to it under incoming President-elect Joe Biden.

"We are deeply concerned that on January 4 in the subterranean uranium enrichment facility of Fordo, Iran, began enriching uranium to a level of 20 per cent," read the statement, distributed by the German Foreign Office. 

"This action, for which there is no credible civilian justification, and which poses significant proliferation risks, is a clear violation of Iran's obligations under the JCPoA and further undermines the agreement," it added.

The European ministers added that Iran's decision "risks jeopardizing the important opportunity for a return to diplomacy with the incoming US administration."

Outgoing US President Donald Trump withdrew his country from the treaty in 2018.

The EU, which is also a party to the deal along with China, on Tuesday vowed to make efforts to uphold the agreement.

'Fatal consequences' of proliferation

German Foreign Minister Heiko Maas, speaking at a conference on nuclear disarmament in Jordan, made an appeal to halve the development of more nuclear weapons around the world.

"We live in a time that has once again developed into a spiral of armament. And if we continue to just sit there and watch, this will have fatal consequences," Maas said.

However, Maas reaffirmed the commitment of Germany as a NATO partner to the principle of nuclear deterrence.

Experts estimate that Germany is storing around 20 atomic bombs at Büchel Air Base in the country's west. Tornado fighter jets belonging to the German Bundeswehr military are stationed at the base that could drop the bombs if ordered. 

The bombs are subject to a dual key system, requiring the simultaneous authorizations of Germany and the US before any action can be taken.

rc/nm (dpa, AP, AFP, Reuters)