Iran is planning a major advancement of its nuclear enrichment programme which will enable it to accelerate the processing of uranium.
The move is likely to increase fears about the ultimate aims of its atomic programme.
The Islamic Republic has told the United Nations atomic watchdog that it plans to install more advanced centrifuges at its main nuclear enrichment facility at Natanz.
The move drew a warning from Washington yesterday, which called it a "further escalation" in the showdown over its atomic programme.
"The installation of new advanced centrifuges is a further escalation and a continuing violation ... of Iran's obligations under relevant United Nations Security Council and IAEA board resolutions," the White House spokesman Jay Carney said.
The defiant plan - likely to alarm the United States, Israel and European nations - coincides with wrangling between Iran and six world powers over the resumption of stalled talks over Tehran's nuclear programme.
However, the decision even drew criticism yesterday from Moscow, a nominal ally that has opposed western-led sanctions against Tehran.
The Russian foreign minister, Sergei Lavrov, said: "We along with other UN Security Council members have called upon the Iranians to freeze enrichment work during negotiations."
Iran's latest nuclear brinkmanship may be aimed at strengthening its bargaining hand at those negotiations with the so-called P5+1, comprising the five permanent members of the UN Security Council and Germany.
Tehran does not want to be seen as entering any talks from a position of weakness after its economy has been battered by US-led sanctions against its vital oil and banking sectors.
The Iranian regime is gearing up for presidential elections in June that could make it difficult for Tehran to make major decisions on its nuclear programme before then.
However, some analysts argued that Iran's plans are neither a "game-changer" nor a bargaining tactic. Scott Lucas, an Iran expert at Birmingham University in England, said: "Of course Iran would want to introduce a more viable centrifuge if it could. Any talk of this being a military development is an exaggeration."
Iran plans to install the new generation of centrifuges at its main enrichment plant near the central town of Natanz, according to a letter Tehran sent last week to the Vienna-based International Atomic Energy Agency (IAEA). The letter came to light after the IAEA notified its members on Wednesday.
Most of the centrifuges there are of the older and less reliable IR-1 models developed in the 1970s. The new IR-2 machines could increase Iran's stockpile of enriched uranium at two to three times the present rate, experts said.
The Natanz plant is used to purify uranium to less than 5 per cent, the level needed to fuel nuclear power plants. Of far greater concern to the West is Iran's underground site at Fordow, which enriches uranium to 20 per cent. It is only a short technological leap to the 90 per cent level needed for a bomb.
But even at Fordow, Iran has been careful not to generate enough fissile material that could warrant an Israeli military strike.
Fordow "has increasingly been the focus of concern about Iran's capability, but a technological breakthrough at the much bigger Natanz plant might still be more provocative", said Mark Hibbs, a nuclear expert at the Carnegie Endowment think tank in Washington.
Iran insists that its nuclear ambitions are for civilian and peaceful purposes only - to generate electricity and provide medical isotopes for cancer patients. Tehran has about 10,000 centrifuges at Natanz, with another 3,000 at Fordow.