VIENNA — The U.N. nuclear agency on Monday confirmed that Iran has begun enriching uranium at an underground bunker to a level that can be upgraded more quickly for use in a nuclear weapon than the nation's main enriched stockpile.
Comment from the International Atomic Energy Agency came after diplomats said that centrifuges at the Fordo site near Iran's holy city of Qom are churning out uranium enriched to 20 percent. That level is higher than the 3.5 percent being made at Iran's main enrichment plant and can be turned into fissile warhead material faster and with less work.
"The IAEA can confirm that Iran has started the production of uranium enriched up to 20 percent ... in the Fordow Fuel Enrichment Plant," said an agency statement, which used the alternate spelling for the site.
The move was expected, with Tehran announcing months ago that it would use the Fordo facility for 20 percent production. Iran began to further enrich a small part of its uranium stockpile to nearly 20 percent as of February 2010 at a less-protected experimental site, saying it needs the higher grade material to produce fuel for a Tehran reactor that makes medical radioisotopes for cancer patients.
But with the time and effort reduced between making weapons-grade uranium from the 20-percent level, the start of the Fordo operation increases international fears that Iran is determined to move closer to the ability to make nuclear warheads — despite insistence by the Islamic Republic that it is enriching only to make reactor fuel.
Its dismissal of findings by the International Atomic Energy Agency of secret experimental work on a nuclear weapons program also worries the international community.
British Foreign Secretary William Hague called the move "a provocative act which further undermines Iran's claims that its program is entirely civilian in nature."
Tehran's "claim to be enriching for the Tehran Research Reactor does not stand up to serious scrutiny," he said in a statement. Hague said that Iran "already has sufficient enriched uranium to power the reactor for more than five years and has not even installed the equipment necessary to manufacture fuel elements" out of the enriched material.
Iran recently threatened to blockade the Strait of Hormuz, an important transit route for almost one-fifth of the oil traded globally. Tehran also has been angered by the West's efforts to sanction Iran over its nuclear program, including a possible ban on European imports of Iranian oil.
Fordo's location increases concerns.
The facility is a hardened tunnel and is protected by air defense missile batteries and the Revolutionary Guard. The site is located about 20 miles (32 kilometers) north of Qom, the religious nerve center of Iran's ruling system. The semiofficial Mehr news agency quoted Iran's nuclear chief, Fereidoun Abbasi, as saying Sunday that "the enemy doesn't have the ability to damage it."
Built next to a military complex, Fordo was long kept secret and was only acknowledged by Iran after it was identified by Western intelligence agencies in September 2009.
Hague said Fordo's size — it is too small for an industrial enrichment complex of the type Iran says it needs to make fuel — "location and clandestine nature raise serious questions about its ultimate purpose."
U.S. State Department spokeswoman Victoria Nuland also questioned Iran's motives.
"When you enrich to 20 percent, there is no possible reason for that if you're talking about a peaceful program," she told reporters. "So it generally tends to indicate that you are enriching to a level that takes you to a different kind of nuclear program."
Two diplomats spoke to The Associated Press on condition of anonymity because their information was confidential and based on an inspection of Fordo last week by the International Atomic Energy Agency.
They said 348 machines were operating at Fordo in two cascades — the linked up configuration needed to enrich. Two other cascades were nearly assembled but not working, they said.