Iran has suggested that France monitor its nuclear programme, by setting up a nuclear fuel consortium inside Iran.
Mohammad Saeedi's plan would still see uranium enriched in Iran
The announcement was made by the deputy head of Iran's atomic energy agency. France said Iran's offers had to go through the EU's foreign policy chief.
But Javier Solana has concluded that Iran is unlikely to suspend nuclear enrichment, said a senior UK official.
Key world powers have agreed to seek a new UN Security Council resolution to impose sanctions, the official said.
The official stressed that this did not prevent further negotiation with Iran to try to persuade it of the benefit of complying with UN requirements to halt their nuclear programme.
The deputy director of Iran's atomic energy agency, Mohammad Saeedi, told French radio that a solution to the nuclear issue could be a consortium with France to enrich uranium in Iran.
"That way France... could control in a tangible way our enrichment activities," Mohammad Saeedi, deputy chief of Iran's Atomic Energy Organization, told France-Info radio.
Mr Saeedi presented this as a new idea, but more than a year ago Iran's president suggested foreign companies should enter into joint ventures with Iran to develop its nuclear power industry, says the BBC's Tehran correspondent Frances Harrison.
Iran has given out confusing and conflicting signals about how far it is willing to go in what many suspect may be a deliberate attempt to delay, says our correspondent.
France said it was taken by surprise by the latest Iranian move.
"There is a channel of dialogue with the Iranians" that must pass through Mr Solana, said Jean-Baptiste Mattei, a spokesman for the French foreign ministry.
"It's through this channel we await a response from the Iranians on the suspension" of uranium enrichment, as demanded by the UN Security Council, Mr Mattei told reporters.
Speaking in Helsinki, Mr Solana said the Iranian offer was "something we have to analyse in greater detail".
He described a telephone conversation with Iran's nuclear chief Ali Larijani as "cordial and constructive".
But he added: "We still have some elements that need to be agreed. We will continue talking."