Iran has begun enriching uranium at a heavily fortified underground site, the International Atomic Energy Agency (IAEA) said in an announcement that drew immediate US condemnation.
"Iran has started the production of uranium enriched up to 20 percent" in the Fordow Fuel Enrichment Plant, IAEA spokesman Gill Tudor said in an e-mail today. "All nuclear material in the facility remains under the agency's containment and surveillance."
US State Department spokeswoman Victoria Nuland said the enrichment represented an intensification of Iranian violations of United Nations agreements on its nuclear program.
"This is a further escalation of their ongoing violations with regard to their nuclear obligations," Ms Nuland said today. "We call on Iran once again to suspend enrichment activities."
IAEA inspectors conduct safeguard inspections of the facility in Fordow, near the holy city of Qom. Western intelligence reports revealed Iran was secretly building the plant in 2009, raising concerns about its purpose.
"The worry was that it would be this covert enrichment site that would allow Iran to produce weapons-grade uranium fairly quickly without anyone knowing it was taking place," David Albright, president of the Institute for Science and International Security, a Washington nonprofit group, said today in a telephone interview.
The IAEA has asked Iran to clarify the circumstances that led to the plant's construction. Nuland said Iran was taking the "next step" and couldn't have civilian uses in mind.
"When you enrich to 20 per cent there's no possible use if you're talking about a peaceful purpose," Ms Nuland said. "You're enriching to a level that takes you to a different kind of nuclear program."
While Iran says it needs the enriched uranium for civilian use in a research reactor, Mr Albright said Iran has already produced enough such fuel to serve that purpose for several years.
Stockpiling 20 per cent enriched uranium would make it that much easier to get to the next step of 60 per cent, and from there to 90 per cent enrichment that is ideal for creating weapons, he said. "So that if they do decide they want nuclear weapons, it's easy to do," he said.
The activities at Fordow would let Iran "build nuclear weapons relatively quickly and in facilities that are relatively hard to destroy militarily," Mr Albright said. Iran has repeatedly denied any ambition to build a nuclear weapons program.
Ms Nuland said the US was open to talks with Iran if it would "come clean" about its nuclear program. Tensions between Iran and the West have escalated as the US moves to sanction Iran's central bank and the European Union considers an embargo on Iranian oil.
Iranian Vice President Mohammad Reza Rahimi said on December 27 that his nation would block oil shipments through the Strait of Hormuz if sanctions are imposed, the Islamic Republic News Agency said.
The Strait is a transit point for one fifth of oil traded worldwide. Jay Carney, the White House press secretary, said moves on additional sanctions "must be timed and phased" to avoid damage to oil markets.
Agencies