"We call on Iran to reverse all steps taken since July and return to full compliance with its commitments," Maas told reporters in Berlin.

Tehran announced in July that it would resume enrichment, after the United States walked away from an international deal on curbing Iran's nuclear ambitions.

Maas noted however that other signatories of the accord are still holding up their end of the deal, and warned Iran against further endangering the pact.

"Our aim is to maintain the nuclear agreement. We have always fully implemented our commitments and Iran must now urgently relent in order to ease tensions," Maas said.

A spokesman for the Iranian atomic energy agency said Wednesday said Iran's Fordow plant would begin enriching uranium from midnight (2030 GMT).