The apparent breakthrough is likely to heighten international tensions over Iran's alleged pursuit of nuclear weapons, with the United States saying the move showed Iran was "moving in the wrong direction." Making the announcement in a televised address on Tuesday, Mahmoud Ahmadinejad also said that Iran was determined to achieve enrichment on an industrial scale.

"I am officially announcing that Iran has joined the group of those countries which have nuclear technology. This is the result of the Iranian nation's resistance," Ahmadinejad said in the address from the northeastern city of Mashhad. "Based on international regulations, we will continue our path until we achieve production of industrial-scale enrichment."

The announcement came shortly before Mohamed ElBaradei, the head of the United Nations' nuclear watchdog, was due to visit Iran for talks aimed at resolving an international standoff over its nuclear programme. ElBaradei was expected to arrive in Tehran on Wednesday at the earliest.

'Peaceful' technology

The UN Security Council has demanded that Iran stop all nuclear enrichment processes by April 28, because of suspicions by several mainly Western countries that the programme is designed to develop nuclear weapons. Apparently rejecting that call, Ahmadinejad said that the West must respect Iran's right to peaceful atomic technology.

"I am advising them to respect the Iranian nation's right to nuclear technology and not to create an ever-lasting hatred of themselves among our nation," Ahmadinejad said. "We have repeatedly said that Iran does not need weapons of mass destruction." His announcement came only hours after Akbar Hashemi Rafsanjani, a former president, disclosed that Iran was successfully producing enriched uranium.

Expansion

"We operated the first unit which comprises 164 centrifuges, gas was injected, and we got the industrial output," Rafsanjani told Kuwait's KUNA news agnecy. "There needs to be an expansion of operations if we are to have a complete industrial unit; tens of units are required to set up a uranium enrichment plant."

Commenting on the Iranian claims, the Bush administration said the move showed "that Iran is moving in the wrong direction." "Defiant statements and actions only further isolate the regime from the rest of the world," said Scott McClellan, the White House spokesman. He added that if it persisted, America would discuss possible next steps with the UN Security Council.

Western fears

The West fears that Iran could be using its nuclear power programme as a smokescreen to build atomic bombs, but Tehran denies this. The International Atomic Energy Agency said last month that Iran had started testing 20 centrifuges. Gholamreza Aghazadeh, the head of Iran's Atomic Energy Organisation, said in February that Iran had started work on uranium fuel, but using only a few centrifuges. He said then that Iran was months away from operating a full cascade.

On Tuesday, however, he confirmed the enrichment announcement. "I am proud to announce that we have started enriching uranium to the 3.5% level," he said in a televised address. He said that the pilot enrichment plant in Natanz, south of Tehran, had started working on Monday. Each centrifuge chain contains 164 units. Such cascades refine uranium gas into fuel for power stations, or if highly enriched - to 90% - for bombs. About 1,500 centrifuges running optimally for a year could yield enough material for a bomb, scientists say.

Russia slams Iran nuclear move

Russia has criticised Iran's claim to have successfully enriched uranium, calling it a "step in the wrong direction" and demanding Tehran stops further nuclear enrichment immediately. The stern words from Moscow echo earlier remarks from the Bush administration which said Iran risked forcing the UN security council into further action. A foreign ministry spokesman, Mikhail Kamynin, was quoted by the ITAR-TASS news agency as saying Iran's announcement "runs counter to the resolutions of the IAEA board of governors and the declarations from representatives of the United Nations Security Council."

Kamynin said Russia supported the planned visit of Mohamed ElBaradei, the head of the IAEA, to Iran on Wednesday to undertake a fact-finding mission before the April 28 deadline imposed by the UN for Iran to cease all uranium enrichment. "We hope that Iran correctly understands the concern of the international community and takes practical steps to implement IAEA decisions," he said. "These include a call for suspension of all uranium enrichment work, including scientific research."

Diplomatic blow

Confirmation from Iran that it has successfully enriched uranium will come as a blow to Russian diplomatic efforts to avert the imposition, advocated by the US, of sanctions on Iran. Moscow had offered to aid Iran's nuclear programme by helping it to enrich uranium on Russian soil for shipment to Iranian power plants. That offer now seems unlikely to be taken up.

Iran has traditionally regarded Russia as a main nuclear ally and several officials in Tehran have predicted that Russia will veto any punitive action by the UN security council. The US for its part said it could not verify Iran's claims, but that even if true, it would take years before it had the capability for nuclear weapons.

White House spokesman, Scott McClellan said: "If the regime continues to move in the direction that it is currently, then we will be talking about the way forward with the other members of the Security Council and Germany about how to address this going forward."

'National right'

China, which is also believed to be opposed to sanctions, urged a diplomatic solution to the row. "We still believe that negotiations and a diplomatic solution are the best way out of it," Wang Guangya, China's envoy to the United Nations, said in New York in comments carried by the official Xinhua news agency.

It was not clear if Wang was responding directly to Iran's announcement. Iran has said it will not back from what it says is a national right to enrich uranium to fuel nuclear power stations. Many Western countries believe Tehran is seeking to acquire atomic warheads.

"Based on international regulations, we will continue our path until we achieve production of industrial-scale enrichment," Mahmoud Ahmadinejad, the Iranian president, told officials and some ambassadors from regional states gathered in the northeastern city of Mashhad on Tuesday.

The level of enrichment needed to trigger the nuclear chain reaction that detonates bombs is far higher than the 3.5% Iran says it has reached. It would take Iran years to yield enough highly enriched uranium for one bomb with its current cascade of 164 centrifuges. But Tehran has told the IAEA it will start installing 3,000 centrifuges later this year, enough to produce material for a warhead within a year.