"The marathon of negotiations continues," Iranian Deputy Foreign Minister Seyed Abbas Araqchi said after four hours of negotiations with his French, British, and German counterparts on Thursday.
He added "We are trying to reach a preliminary political agreement by March".
Deputy foreign ministers from Iran and the European members of the Group 5+1 (also known as P5+1 and E3+3) held one-day nuclear talks in Istanbul on Thursday.
The talks were part of regular meetings between Tehran and the world powers aimed at settling a decade-long standoff on Iran's nuclear case.
"Simultaneous negotiation with six countries is difficult,” he stressed, noting that the six countries have diverse opinions on the issue.
The senior negotiator said the Iranian delegation held good negotiations with the three European countries on Thursday, days after their bilateral talks with the Americans.
The Iranian deputy FM added that talks with the Russian and Chinese sides are also held regularly.
He further described the negotiations as "very useful”, but noted at the same time that it is too early to say that progress has been made.
Iran and 5+1 are in talks to hammer out a final agreement to end more than a decade of impasse over Tehran’s nuclear energy program.