Foreign Ministry spokesman Hamid Reza Asefi said on Sunday that "the atmosphere" was better than before.
"We hope to reach concrete results ... on 19 April," he said, referring to a meeting of experts from Europe and Iran ahead of a steering committee meeting on 29 April to "to find future solutions".
"The prospects are better than before and we hope we will be able to take a positive step" in the next meetings, Asefi said.
Iran has been negotiating since December with Britain, France and Germany to win trade, security and technology rewards in return for giving guarantees that it is not trying to develop nuclear weapons.
Tehran, which insists its nuclear programme is for peaceful purposes only, agreed in November to suspend enrichment activities as a goodwill gesture for a maximum of six months, but the Europeans want the suspension to become permanent, a demand the Iranians have termed "absurd".
Iran says it has the right to enrich uranium to low levels to produce atomic fuel for civilian power stations.
Highly enriched uranium can provide the core for an atomic bomb.
Asefi insisted Iran would not give up uranium enrichment, saying that the current freeze was "temporary and for a short period".
In France last week, Iranian President Muhammad Khatami said he expected significant headway at the next meeting of Iranian and European negotiators, saying the two sides were closer to a solution than before.
"I think we have made positive steps. Iran has proposed a global plan to settle this issue," he said.