Iran's controversial uranium-enrichment programme - the key to its controversial nuclear plans - shuddered to a halt for at least one day earlier this month, a confidential United Nations report revealed last night.
The UN's nuclear watchdog, the International Atomic Energy Agency (IAEA), gave no reason for the mysterious outage on November 16. But there were credible reports that the havoc was caused by an ingenious computer virus, known as Stuxnet.
Tehran, however, vehemently denied that its cherished nuclear programme had fallen victim to a cyber attack.
Iran's nuclear chief, Ali Akbar Salehi, said that unspecified "enemies" - widely assumed to be Israel or the United States - had attempted to infect Iran's nuclear activities with the self-replicating Stuxnet worm 18 months ago. But, he claimed, they were foiled by vigilant young Iranian computer experts. The virus has been described as the world's first cyber-guided missile.
"Fortunately the nuclear Stuxnet virus has faced a dead end … and the desires and dreams of the enemies have not become true," Mr Salehi declared.
Iran's adversaries, he said, had only unveiled details of the cyberworm in June after their schemes were thwarted.
The IAEA report also said that it was concerned about possible activity in Iran to develop a nuclear payload for a missile.
Experts believe that the Stuxnet worm was specifically designed to sabotage Iran's centrifuges so that they spin out of control.
Technical problems afflicting Iran's nuclear programme would buy more time for a diplomatic solution to the prolonged and tense standoff over the Islamic Republic's atomic drive, which the West suspects is aimed at weapons development.
Tehran insists its uranium enrichment is designed solely to fuel civilian nuclear power plants to generate electricity, saving the country's vast oil and gas reserves for lucrative export.
No country has claimed responsibility for developing Stuxnet, which is the first computer worm to target control systems in industrial plants.
Iran seemingly is concerned that admitting its enrichment programme has suffered crippling technical setbacks could weaken its negotiating hand in long-stalled nuclear talks with world powers that are due to resume on December 5.
Olli Heinonen, who was the IAEA's deputy director until August, said the Stuxnet worm could for "sure" be one of the problems causing delays in Iran's nuclear programme, although "there is no evidence that it was".
Serious technical snags have long bedevilled work at Iran's underground uranium-enrichment plant in the central town of Natanz.
But it is not clear whether the problems were the result of sanctions, poor design or sabotage.
Mr Heinonen said that 3,772 centrifuges at the heavily fortified facility were operating, while 5,084 were idle. "This indicates there is a problem," he added drily.
And, he continued, the Islamic republic is apparently having great difficulty in developing a second-generation centrifuge able to enrich uranium more speedily. Iran's centrifuges are modelled on a Pakistani copy of a decades-old Dutch design.
International sanctions, Mr Heinonen said, could be stymying Tehran's attempts to buy raw materials, such as high-strength carbon, to upgrade its centrifuges.
Tehran recently acknowledged that the Stuxnet worm had infected personal computers at its first nuclear power plant on Iran's southern Gulf coast city of Bushehr, but denied it had damaged operations there.
Most nuclear experts regard the Bushehr generator, which is due to start producing electricity in January, to be of little use to Iran in any alleged weaponisation drive. The facility is under strict international supervision and runs on fuel imported from Russia, which helped build the plant.
Even so, the Associated Press cited an official from an IAEA member country suggesting that the Stuxnet virus could result in a meltdown at the Bushehr reactor when it comes online.
