The bleak statement from the British embassy in Tehran comes amid increasing pessimism among European Union diplomats, who are trying to secure guarantees the clerical regime will not use an atomic energy drive as a cover for nuclear weapons developments.

"The UK regrets recent comments by Dr Larijani, suggesting that Iran would shortly resume centrifuge activity," the embassy said, referring to Iran's top nuclear negotiator and hardliner Ali Larijani.

Larijani asserted last week that Iran could soon resume making centrifuges and their parts and conducting "research", arguing such activities were legal and outside the scope of any future talks with Britain, France and Germany.

Centrifuges are spun at supersonic speed to enrich uranium gas -- which Iran is already producing in large quantities -- to make reactor fuel, but the enrichment process can be extended to make the core of a nuclear bomb.

"The European side made clear in Vienna that any resumption of enrichment or enrichment related activity would seriously aggravate the situation," Britain said, pointing to "urgent proliferation-related concerns given Iran's history of concealment and involvement with clandestine proliferation networks."

With the two sides scheduled to meet over the coming weeks, Britain complained that Larijani's comments "seem to be aimed at prejudging these discussions and preventing the possibility of finding a basis for negotiations".

Iran insists it only wants to generate electricity.

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