Pakistan has reportedly agreed to hand uranium-enriching components over to UN inspectors, which could help in an inquiry into Iran's nuclear programme.
Critics ask why fuel-rich Iran needs nuclear energy
It earlier admitted the former head of its own programme, Abdul Qadeer Khan, had sold Iran similar centrifuge parts.
Diplomats close to the inquiry told reporters that Pakistan would give them to a UN laboratory in Austria.
They will then be compared with centrifuges found in Iran with suspicious uranium traces.
"These may hold the crucial fingerprints, the DNA, of the uranium traces found on equipment in Iran," a diplomat, who asked not to be named, told Reuters news agency.
Diplomats said the parts to be sent to Austria would come from the same group of centrifuges as those sold to Iran.
"The components will be secretly flown to Vienna in the middle of the night," one said, without giving further details.
The UN's Vienna-based International Atomic Energy Agency (IAEA) has been investigating Iran's nuclear programme for the past two years.
While it has found no proof that Iran plans to build nuclear weapons, it has also been unable to confirm that the programme is entirely peaceful, as Iran insists.
Washington has accused Iran, a state already rich in gas and oil, of pursuing atomic energy as a screen to develop nuclear weapons.
In 2003, the IAEA found traces of uranium in Iran that had been enriched to various levels, some of them close to what would be useable in weapons.
Fears then arose that Iran had been secretly seeking to purify uranium for use in weapons.
Iran blamed the traces on contaminated centrifuge components it had acquired second-hand from Pakistan.