Iran handed over the letter to European Union foreign policy chief Catherine Ashton, who handles contacts with Tehran on behalf of the six major powers, on Wednesday.

“Madame Ashton received a letter from Mr.(Iranian chief nuclear negotiator Saeed) Jalili responding to her letter in October last year,” Juppe told reporters during a visit to Vienna.

“In our eyes it remains ambiguous, but constitutes the start of opening up from Iran which says it is ready to talk about its nuclear program.”