Iran has acknowledged to the UN its uranium enrichment centrifuge program is based on a European firm's designs that appear identical to ones used in Pakistan's quest for an atom bomb, diplomats say.
Tehran, accused by Washington of seeking to develop nuclear weapons, told the UN nuclear agency it got the blueprints from a "middleman" whose identity the agency had not determined, a Western diplomat told Reuters on condition of anonymity.
It was unclear where the "middleman" got the drawings. The UN's International Atomic Energy Agency (IAEA) has said in a report that Iran told the IAEA it got centrifuge drawings "from a foreign intermediary around 1987."
Centrifuges are used to purify uranium for use as fuel or in weapons. Experts say the ability to produce such material is crucial for an arms program and is the biggest hurdle that any country with ambitions to build a bomb must overcome.
Several diplomats familiar with the IAEA said the blueprints were of a machine by the Dutch enrichment unit of the British-Dutch-German consortium Urenco -- a leader in the field of centrifuges.
Iran's ambassador to the IAEA, Ali Akbar Salehi, told Reuters he had no knowledge that a Urenco design had been used by Iran. "This is new information to me," he said.
In a statement to Reuters, Urenco said it had not supplied any centrifuge know-how or machinery to Iran.
Pakistan, which nonproliferation experts and diplomats say used the Urenco blueprint, and Iran have repeatedly denied any cooperation in the nuclear field.
Iran has long insisted its centrifuge program is purely indigenous and that it has received no outside help whatsoever.
The father of Pakistan's atom bomb, Abdul Qadeer Khan, worked at the Urenco uranium enrichment facility in the Dutch city of Almelo in the 1970s.
After his return to Pakistan he was convicted in absentia of nuclear espionage by an Amsterdam court, but the verdict was overturned on appeal.
He has acknowledged he did take advantage of his experience of many years of working on similar projects in Europe and his contacts with various manufacturing firms.
But David Albright, a former UN weapons inspector and head of the Institute for Science and International Security think tank, said: "Khan is widely believed to have taken these drawings and developed them."