Iran and leading EU nations have failed to reach agreement in talks about Tehran's nuclear ambitions.
Tehran says its right to nuclear power is non-negotiable
The EU Three - France, Germany and the UK - want Iran to abandon its uranium enrichment and reprocessing activities.
They are offering Tehran economic, political and technological incentives for giving up the programme.
Iranian negotiators, who insist Iran has the right to a civilian nuclear programme, said all sides have agreed to meet again in the coming weeks.
Iranian nuclear negotiators had said on Tuesday that Tehran would reconsider its position on the talks if no real progress was made.
Wednesday's meeting offered a chance to review progress made in working groups over three months.
At the end of the talks, Sirus Nasseri, a senior Iranian negotiator, confirmed the four parties would meet again, adding: "Each side still has its own views."
The EU Three recently admitted that progress had not been as rapid as they might have wished.
Nevertheless, the BBC's Pam O'Toole says they appear encouraged that Iran is willing to suspend uranium enrichment while negotiations are under way.
Publicly, Iranian officials have been dismissive about a US offer of limited economic incentives.
The Europeans have warned they would back US moves to take Tehran to the UN Security Council if Iran breaches agreements or resumes uranium enrichment during the talks.
Iran maintains its nuclear programme is entirely peaceful, but Washington suspects it of secretly trying to build a nuclear weapon.