By Bethany Bell
BBC News, Vienna
Iran's chief negotiator to the United Nations nuclear agency says Tehran is committed to the freeze on uranium enrichment agreed earlier this month.
Iran is seeking an amendment to a deal reached last week
Hossein Moussavian told the BBC he was optimistic an agreement would be reached on Iran's request to use 20 enrichment centrifuges for research.
Tehran agreed to halt its enrichment programme last week.
But its demand to use the centrifuges has threatened to collapse the deal, with key EU nations against the move.
France, Germany and Britain - the three EU countries that helped bring about the suspension - reportedly refused the request.
The board of the International Atomic Energy Agency (IAEA) is currently meeting to discuss Iran's nuclear programme, amid suspicions that Tehran is trying to develop atomic weapons.
Iran had accepted the suspension of its uranium-enrichment activities, Mr Moussavian told the BBC.
But he added that the suspension should be seen as a confidence-building measure and not as a legal obligation for Iran.
Iran's demand for 20 enrichment centrifuges for research was not an important issue, Mr Moussavian said, stressing that there had been progress in negotiations with the Europeans.
"We have already agreed to have suspension of enrichment and related activities," Mr Moussavian told the BBC.
"As I said, this is not a very important issue, this - we believe this is a technical issue which we are... under discussion with IAEA - hopefully we will resolve."
The dispute over the centrifuges has threatened the hard-won agreement between Iran and the Europeans.
The Europeans say all of Iran's enrichment-related activities - including the 20 research centrifuges - must be suspended.
Enrichment is a process of purifying uranium for use as fuel in power plants or, when very highly enriched, in weapons.
Discussions among members of the IAEA's board of governors are likely to continue for some time to come.
The United States has accused Iran of trying to secretly develop nuclear weapons - a charge Tehran rejects.