Iran has agreed in principle on a joint venture with Russia to enrich uranium.
Western powers suspect Iran's nuclear ambitions are not peaceful
But further talks are needed, said the head of Iran's nuclear agency, Gholamreza Aghazadeh.
The Russian compromise proposal is that Iran move all the sensitive parts of its nuclear programme to Russian soil to allay Western concerns.
But it is thought unlikely Iran would agree to this. Tehran says it will not give up its current enrichment programme resumed earlier this month.
Mr Aghazadeh was speaking at a news conference in the southern city of Bushehr with his visiting Russian counterpart, Sergei Kiriyenko.
He said any deal to form a joint company for producing nuclear fuel would have to go further and be part of a wider package if it were to resolve the current crisis.
It appears Iran is looking for a wider compromise that would allow it to keep its nuclear research programme, says the BBC's Frances Harrison in Tehran.
Mr Kiriyenko said he agreed all countries had the right to nuclear technology, but added that the international community also had the right to objective guarantees that Iran was not seeking nuclear weapons.
The Russian proposal has been seen by many as a last chance for Iran to compromise with the UN nuclear agency, the International Atomic Energy Agency.
On 6 March the agency is due to issue a report that might move the whole issue to the UN Security Council.
Iran has previously insisted that it will not give up the right to enrich uranium on its own territory.
The agency reported Iran to the Security Council in January over a lack of co-operation and transparency in its nuclear activities.
Western powers are concerned Iran aims to develop nuclear weapons, but Tehran says its programme is not military.
Iran resumed small-scale uranium enrichment earlier this month.
Enrichment can produce fuel for either civilian nuclear reactors or nuclear bombs.
The nuclear crisis has intensified since Iran resumed nuclear activity last summer after a two-and-a-half year freeze.