"There are many ambiguities in the European proposal ... We are waiting for an answer from the Europeans on our questions before we can decide (to accept it)," Hossein Moussavian told AFP by telephone from Vienna.

Talks are to resume at the headquarters of the International Atomic Energy Agency (IAEA) in the Austrian capital on Wednesday, but the spokesman said the European proposal "must be more balanced".

"The assurances, commitments and confidence-building measures must be reciprocal. The nature of the cooperation must be defined and there must be a guarantee for implementing the outcome of the talks," he said.

"The period of negotiations cannot be limitless. We need some months for talks to see if we can arrive at an agreement or not," stressed the spokesman.

"If the Europeans accept our principles and criteria, I am not pessimistic about the chances of reaching a compromise, but we need several more meetings," he said.

On Thursday, Britain, France and Germany offered Iran a deal under which Tehran would receive valuable nuclear technology if it indefinitely suspended all uranium enrichment activities, a key stage in the nuclear fuel cycle.

The EU "big three" hope that if Iran agrees to the deal it will be possible to stave off US demands for Iran's nuclear programme to be sent before the UN Security Council.

The IAEA, the UN's nuclear watchdog, has given Iran a November 25 deadline to allay concerns about its nuclear activities.

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