Foreign Minister Heiko Maas defended the 2015 agreement under which Iran drastically scaled back its nuclear programme in return for sanctions relief.

EU diplomatic chief Federica Mogherini said the bloc was determined to preserve the "full implementation" of the deal, saying it was vital to European security.

"Together with the Brits, French and the entire EU we have found ways to keep Iran in the nuclear agreement until today," Maas told the Munich Security Conference.

A day earlier, Pence accused Tehran of planning a "new Holocaust" with its opposition to Israel and regional ambitions in Syria, Lebanon, Iraq and Yemen.

Maas said that "our goal remains an Iran without nuclear weapons, precisely because we see clearly how Iran is destabilising the region".

Without this agreement, "the region will not be safer and would actually be one step closer to an open confrontation," he added.

Speaking at the same conference, Mogherini said the deal must be preserved, insisting that for Europe "it's a matter of security".

"So you can count on the fact the European Union and its member states will continue to serve the interests of security and non-proliferation... preserving the full implementation" of the deal, Mogherini said.

Pence at a conference on the Middle East in Warsaw on Thursday denounced the retention by the Europeans of the nuclear agreement.

He also criticised the initiative of France, Germany and Britain to allow European companies to continue operating in Iran despite US sanctions.