Vienna • Iran has effectively shut down a probe of a site suspected of being used for work on nuclear weapons development while doubling the number of machines it could use to make the core of nuclear warheads at an underground bunker safe from airborne attack, the U.N. nuclear agency said in a report Thursday.
Senior diplomats familiar with the International Atomic Energy Agency's latest report called both developments troubling, while cautioning that it was unclear whether many of the more than 2,000 centrifuges now installed at the Fordo site were operational. They noted that agency inspectors did not have access to check their inner workings.
They also said it was unclear what the ultimate use of the machines would be, if and when they are turned on. Iran is enriching uranium at a level that could be used for reactor fuel as well as grades closer toÂ the level used for nuclear warheads, and the officials said Iranian officials had not said what level the centrifuges now installed but not working would be used for.
The diplomats demanded anonymity because they were not authorized to comment on the confidential report.
Importantly, the report noted that Iran had not increased either low or higher-level uranium enrichment. It noted that less than 700 of the machines all producing higher level material at 20 percent were operating at Fordo, and less than 10,000 were operating at another site used for turning out lower-level enriched uranium. Those are approximately the same number as mentioned in the agency's last report in May.
Iran denies any interest in nuclear arms, insisting it is enriching uranium only to make reactor fuel, medical isotopes and for scientific research. Still, enriched uranium at all levels can be turned into weapons-grade material, and Tehran has refused to stop enriching uranium, despite increasingly severe international sanctions and outside offers of enriched material for its stated needs raising concerns about its ultimate nuclear aims.
As signs grow that international efforts are failing to engage Iran diplomatically on its nuclear program, so are threats of attack from Israel, which says it will not tolerate an Iran armed with nuclear weapons.
Ayatollah Ali Khamenei, Iran's supreme leader, denied his country wanted such arms, describing the pursuit of nuclear weapons on Thursday as aÂ "big and unforgiveable sin." But he insisted Tehran will not abandon its "peaceful" atomic program.
"I declare that the Islamic Republic of Iran has never been after nuclear weapons and it will never abandon its right for peaceful use of nuclear energy," KhameneiÂ told a summit of 120 nations that call themselves nonaligned.
Khamenei singled out the United States, which accuses the Islamic Republic of trying to reach the nuclear weapons threshold, calling Washington's stance a "bitter satire" because of the size of America's nuclear arsenal and its use of atomic bombs against Japan during World War II.
Khamenei, who has final say in matters of state, has denied that Iran harbors nuclear weapons aspirations before. But aside from enrichment, suspicions that Tehran is working secretly on developing nuclear arms have also added to international concerns about its intentions.
Thursday's report confirmed that a building at Iran's Parchin military installation southeast of Tehran, which was suspected of having been used for nuclear weapons-related experiments, has been covered with pink shrouding. That effectively blocks the U.N. agency's attempts to monitor a suspected cleanup of the site.
TheÂ agency has tried and failed to gain access to the site since February. When it does, "its ability to conduct effective verification will have been significantly hampered" because of the alleged cleanup and then the covering of the site, said the confidential report circulated among the IAEA's 35 board member nations.