Nuclear talks between world powers and Iran have not progressed as much as hoped for after three weeks of negotiations and there is still no understanding on the most difficult issues, a European diplomatic source said on Saturday.
"We have much work, and little time, left. Against that background, we would have hoped for more progress this week," the source said after talks broke off for a week. "We have yet to come to an understanding on the most critical points."
The source added that success was still possible, although not guaranteed.