Iranian state television on Friday denied reports that Tehran had used Chinese uranium gas to accelerate enrichment for its controversial nuclear programme, insisting the gas was home-made.
"At the moment, Natanz enrichment facility uses UF6, uranium hexafluoride gas, produced in (Iran's) Isfahan's UCF (uranium conversion facility) site to carry out the enrichment process," it said, quoting an informed source.
Diplomats in Vienna, where the International Atomic Energy Agency is based, have said Iran used stocks of high-quality uranium gas from China to hasten a breakthrough in enrichment.
"The Iranians ... chose the Chinese feedstock gas because of its quality, which ensures a better (uranium) enrichment process," a diplomat with access to intelligence sources told AFP, under the condition of anonymity.
The diplomat said Iran had "wanted to declare it had done uranium enrichment and were in a hurry," as they wanted to have a fait accompli before the UN Security Council could move against them once an April deadline fell.
The Security Council had given Iran until April 28 to halt enrichment, which makes fuel for nuclear power reactors but can also produce the raw material for atomic bombs.
A second diplomat said that Iran had used UF6 gas supplied by China to feed a 164-centrifuge cascade, or array of machines, that enriches uranium.
Iran began feeding UF6 gas into centrifuges in February, thus beginning the enrichment process, at the facility in Natanz, which is located in the center of the country.