The news shows that Iran is moving towards meeting the claim made in April by its President Mahmoud Ahmadinejad that Tehran had achieved an “industrial scale” of enrichment.
Enrichment is the process that makes fuel for nuclear power reactors or, in highly refined form, the raw material for atom bombs.
A diplomat who closely follows the Iranian program said Iran had not mastered enrichment yet.
“They still have problems, a main one being to run the centrifuges for a long, long period,” the diplomat said. Centrifuges are the machines that spin rotors at supersonic speeds to enrich uranium.
“They are speeding up some centrifuges and beginning to enrich towards an industrial level” at an underground plant in Natanz, said the diplomat, who spoke on condition of confidentiality.
Iran previously had been running centrifuges slowly, as many were breaking down, limiting the production of enriched uranium to what were considered research levels.
Iran is defying demands and sanctions from the UN Security Council for it to suspend enrichment, due to fears that it is secretly developing nuclear weapons.
The UN watchdog International Atomic Energy Agency is to file a report by May 23 on Tehran’s nuclear work, and this could lead to further sanctions.
The US ambassador to the IAEA Gregory Schulte told AFP he could not comment on the agency’s findings as he had not yet been briefed.
But he added: “Iran is trying to create ‘facts on the ground’ but it is also a fact that Iran is increasingly isolated.
“Only sustained pressure, with offer of negotiations, is likely to dissuade Iran from continuing down the current path,” Schulte said.
Iran has made it clear in negotiations with the European Union that its ability to carry out large-scale enrichment must be accepted as part of any eventual deal on Tehran’s nuclear program.
IAEA chief Mohamed ElBaradei said that “from a proliferation perspective, the fact of the matter is that one of the purposes of suspension (of uranium enrichment) — keeping them from getting the knowledge — has been overtaken by events,” an IAEA spokesman reported, saying this wording was agreed on for an article published by The New York Times on Tuesday.
ElBaradei said “the focus should be to stop them from going to industrial scale production,” rather than expecting the Iranians to stop all enrichment.
Iran wants to get 3,000 centrifuges functioning, which could produce enough enriched uranium in a year for an atom bomb, and eventually have 54,000 running in what it says is a peaceful program to generate electricity.
Iran had in April blocked IAEA inspectors from making an unannounced visit to the Natanz bunker site, diplomats said, but the IAEA has denied there were any problems in access to Natanz.
Iran had agreed to unannounced visits, in which it gets two hours rather than a week’s notice of an inspection, in early April in return for IAEA surveillance cameras not being set up, diplomats said.
“The Iranians have allowed the IAEA into Natanz but did not let the inspectors get close to the centrifuges” which are in a huge hall, the first diplomat said.
This prevented the IAEA from obtaining more detailed data in its task of verifying that nuclear material has not been diverted for non-peaceful uses.
After strong pressure from the IAEA, the Iranians accepted an unannounced visit Sunday from inspectors who had arrived in Iran on Saturday evening, a second diplomat said.
The first diplomat said the Iranians had 1,600 centrifuges running, although not all at full speed, and were installing “cascades” of 164 centrifuges at the rate of one cascade about every 10 days.
The IAEA has said the Iranians are enriching to levels corresponding to fuel, which is under five percent refined for the U-235 isotope.
Weapons-grade is over 90 percent.
