Iranian Deputy Foreign Minister Abbas Araqchi met with delegates from the so-called P5-plus-1 -- Britain, China, France, Russia, the United States plus Germany -- to discuss Iran's controversial nuclear program.
He was quoted by the semiofficial Fars News Agency as saying the "discussions were definitely useful."
Iranian officials this week downplayed the prospects for a comprehensive nuclear agreement, while expressing optimism over the potential to formulate a draft.
In November, Iran agreed to suspend some of its nuclear research activity in exchange for modest relief from Western economic sanctions.
Catherine Ashton, the top foreign policy official for the European Union, issued a joint statement Wednesday with Iranian Foreign Minister Mohammad Javad Zarif saying Wednesday's talks were "substantive."
Ashton frustrated Iranian officials last week when she met with female dissidents during her visit to Tehran.
Iran is suspected of pursuing the technology needed to manufacture a nuclear weapon, an allegation it denies.
Another round of talks is scheduled April 7-9 in Vienna.