The foreign minister said the negotiators will "work full time" in the countdown to a June 30 deadline to strike a final deal with the major powers on Tehran's nuclear program.
"We have decided to work full time over the next three or four weeks to explore the possibility of reaching the deal," Mohammad Javad Zarif was quoted by ISNA as telling reporters on Sunday.
Noting that there are numerous differences left to be resolved in the talks, he said, "Efforts will be made in next meetings to minimize these differences and (the results) will be studied in the next ministerial meeting."
Asked to elaborate on the nature of the lingering issues, Zarif said, "They are largely the same issues already announced publicly."
The differences concern both "technical" and "political" aspects, he said, adding, "It is the responsibility of the negotiators to try to help finish drafting the text (of the prospective deal) based on what was agreed in Lausanne and to avoid making excessive demands and raising irrelevant issues."
Iran and the P5+1 (the five permanent members of the UN Security Council plus Germany) managed to hammer out an agreement on the framework of the final accord on April 2 in Lausanne and are negotiating now to complete the text of the deal by the deadline.
A tri-lateral meeting was held between the Iranian delegation led by Zarif, the US delegation headed by US Secretary of State John Kerry and the EU political chief, Helga Schmid, in Geneva on Saturday.
"In the meeting… all issues were fully reviewed once again, yet the differences still remain," negotiator Abbas Araqchi was quoted by IRNA as saying after the meeting.
He also said the talks with the P5+1 will resume on Thursday in Vienna at the level of deputies and experts.
"Secretary Kerry and Foreign Minister Zarif, along with their teams, had a thorough and comprehensive discussion of all of the issues today," a US State Department official said, without elaborating.
This is while a senior US official said earlier there had been substantial progress in negotiations in Vienna in recent weeks on drafting the political agreement and three technical annexes.
The United States has said it will not extend the talks beyond the June 30 deadline.
"We really do believe we can get it done by (June) 30th and we're not contemplating an extension. We just aren't," said the official traveling with Kerry to Geneva, adding that Kerry's schedule for June had been cleared to focus on the talks, Reuters reported.
But France has indicated discussions are likely to slip into July. Araqchi also warned that the deadline might need to be extended.
