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A claim by President Ahmadinejad that Iran has 3,000 working uranium-enriching centrifuges sent a tremor across the world yesterday amid fears that Israel would respond by bombing the country’s nuclear facilities.

Military sources in Washington said that the existence of such a large number could be a “tipping point”, triggering an Israeli air strike. The Pentagon is reluctant to take military action against Iran, but officials say that Israel is a “different matter”. Amid the international uproar, British MPs who were to have toured the nuclear facility were backing out of their Iran trip.

Even before President Ahmadinejad’s announcement, a US defence official told The Times yesterday: “Israel could do something when they get to around 3,000 working centrifuges. The Pentagon is minded to wait a little longer.” US experts say 3,000 machines running for long periods could make enough enriched uranium for an atomic bomb within a year.

Israel responded by serving notice that it would not tolerate a nuclear Iran. “Talks never did, and never will, stop rockets,” said Ehud Barak, the Defence Minister, after talks with the security cabinet.

The US and Western allies believe that Iran is using its civilian nuclear programme as a cover for weapon development. Tehran says that it merely wants to generate electricity.

Concern about Israel’s intentions has been heightened by its recent air strike on a suspected nuclear plant in Syria. In 1981 Israel destroyed Saddam Hussein’s Iraqi nuclear reactor, and as the sole — if undeclared — nuclear power in the region, it now considers Iran the most serious threat to its security. Mr Ahmadinejad has called for Israel to be “wiped off the map”.

Efraim Inbar, of the Begin-Sadat Centre for Strategic Studies in Tel Aviv, said that the figure of 3,000 centrifuges would signal the ability of Israel’s arch-foe to produce the nuclear material needed for a warhead. “I wouldn’t be surprised if we do something if the international community leaves us alone,” he said. “I think we [Israel] are preparing for it. For Israel this is a critical technological moment.”

Tehran says it plans to expand its enrichment programme to up to 54,000 centrifuges at Natanz in central Iran, which would amount to industrial-scale uranium enrichment.

Mr Ahmadinejad, speaking yesterday at a rally, said that UN sanctions had failed to halt uranium enrichment. “The world must know that this nation will not give up one iota of its nuclear rights . . . if they think they can get concessions from this nation, they are badly mistaken,” he said. He has in the past claimed that Iran succeeded in installing the 3,000 centrifuges at its uranium enrichment facility but yesterday’s speech was the first time he had said all of them were now operational.

The International Atomic Energy Authority recently put the figure at closer to 2,000, with another 650 being tested. The IAEA said yesterday: “We will be publishing a report next week. We will not make any comment about this until then.” Javier Solana, the EU foreign policy chief, is shortly to report on Iran’s willingness to give up uranium enrichment in exchange for political and trade incentives.

In London, at least five members of the Commons Foreign Affairs Committee were refusing to take part in the planned trip to Iran, arguing that it would hand the regime a propaganda coup. The visit, to begin on Sunday, would be the first by a select committee since 15 British Service personnel were held in March. That incident and evidence that the regime is supporting insurgencies in Afghanistan and Iraq and planning to build a nuclear bomb has strained relations with Britain.

About eight MPs, from all three main parties, are still planning to spend four days in Iran next week.

Eric Illsley, a Labour MP who is one of those to have pulled out, said: “I really don’t fancy having pictures of me next to an Iranian nuclear facility beamed around the world.”

— Intelligence agencies have begun to vet all foreign postgraduates applying to study sensitive scientific subjects in Britain. The aim is to prevent Iranian students getting expertise in fields related to producing weapons of mass destruction. Sixty Iranians have been refused university places this year.

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