Zarif also added that he was not worried about the attempts by US Congress to impose new sanctions.

"With good will we can reach an agreement within six months," he said in a speech to the German Council on Foreign Relations, adding: "I don't fear a decision in the US Congress ... The US president has promised to veto it."

Zarif was visiting Berlin after meeting US Secretary of State John Kerry and other members of the six powers negotiating with Tehran at the Munich Security Conference at the weekend.

A landmark preliminary deal was clinched on November 24, 2013, between Iran and the six powers – the United States, France, Britain, Russia, China and Germany – in the Swiss city of Geneva.  

Under the Geneva deal, the six countries undertook to provide Iran with some sanctions relief in exchange for Iran agreeing to limit certain aspects of its nuclear activities during a six-month period. It was also agreed that no nuclear-related sanctions will be imposed on Iran within the same timeframe.

RA/NJF