Hossein Moussavian, spokesman for the nuclear negotiating team, told state television that activities would begin when inspectors from the International Atomic Energy Agency arrived at the conversion plant of Isfahan.

"If the Europeans call an extraordinary meeting (of the IAEA's board of governors), that will be a violation of all international rules and they should not expect us to maintain the freeze on our activities at the Natanz enrichment plant," he said.

Iran agreed in November to suspend its enrichment and conversion work -- part of the nuclear fuel cycle -- while negotiations with the Europeans are going on.

But in recent days it has threatened to resume conversion work, triggering warnings from the Europeans that they would halt negotiations and may refer Iran to the UN Security Council for possible sanctions.

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