Ali Akbar Salehi, who is also in charge of Iran's nuclear agency, told national television Tehran offered proposals to remove "fake concerns" over the country's nuclear program, paving the way for a final deal.
"We had reached a sort of deadlock in our technical talks,” Salehi said.
"In those talks, we discussed (uranium) enrichment, Arak research reactor, the issue of research and development, the issue of Fordo nuclear site and some more detailed subjects,” the AEOI chief explained.
"On enrichment and Arak, we have made very good progress. We have replied to their fake concerns... by making technical proposals while also defending our national interests and our nuclear industry," Salehi said.
Over the past two weeks, Salehi held several meetings with U.S. Energy Secretary Ernest Moniz in Geneva and Montreux to discuss details of technical issues.
The Iranian official said the meetings were very productive and good steps were taken, the Tasnim news agency reported.
But the daily Kayhan slammed the negotiations, saying that an American proposal of a 10-year suspension of Iran's uranium enrichment activities is a first step aimed at finally toppling Iran's ruling Islamic government.
Iran and the six-nation group — the U.S., Russia, China, Britain, France and Germany — hope to reach a final agreement by June 30.
On Saturday, top U.S. diplomat John Kerry sought to smooth purported differences with France over nuclear talks with Iran, agreeing with the French that there were still gaps to overcome in the "critical weeks" ahead.