Iran denies claims that it wants to build nuclear weapons

Details of the accord reached in Paris have not been revealed but an Iranian negotiator said fundamental principles had been agreed.

Europe has called on Iran to suspend all its uranium enrichment activities.

Iran denies it has a secret weapons programme, but is threatened with UN action unless it stops its activities.

'Nothing settled'

"Negotiations were very hard and complicated but we reached a preliminary agreement on an expertise level," said Hossein Mousavian, head of Iran's delegation in Paris.

"It is a framework that contains the viewpoints of all sides."

He said the draft had to be approved by the capitals of all four countries involved in the negotiations before it could be made public.

It is still unclear whether the two sides have resolved serious differences.

Europe wanted Iran to suspend enrichment of uranium in return for a trade deal, and an opportunity to buy nuclear fuel.

Iran, however, repeatedly said it would never give up its right to master nuclear technology, though it did indicate it might consider a short-term suspension of enrichment.

A European Union source told Reuters news agency that "nothing is settled" and that the discussions "were difficult, very difficult".

BBC correspondent in Tehran Frances Harrison says given the lack of consensus in the international community about how to tackle Iran, there has been pressure on the Europeans to keep the process of dialogue going.

They had threatened to refer Iran to the United Nations Security Council, but China and Russia indicated they would not back such moves - and they both have veto votes in the Security Council.