US concerned after Iran 'warhead' report

The United States voiced renewed concern yesterday about Iran's nuclear programme after a report by the UN's atomic watchdog suggested Tehran may be working on a nuclear warhead.

"We have ongoing concerns about Iran's activities. We cannot explain why it refuses to come to the table and engage constructively to answer the questions that have been raised," State Department spokesman P.J. Crowley told reporters.

The Vienna-based International Atomic Energy Agency (IAEA) said earlier yesterday in a restricted report that Tehran may be working on a nuclear warhead and had begun enriching uranium at higher levels.

"The information available to the agency... raises concerns about the possible existence in Iran of past or current undisclosed activities related to the development of a nuclear payload for a missile," the watchdog's chief Yukiya Amano wrote in his first report to its board of governors.

The language of the report was much more blunt than that used by Amano's predecessor, Egyptian Mohamed ElBaradei, who stepped down as head of the IAEA at the end of November.

The Vienna-based IAEA has been investigating for a number of years intelligence reports claiming Iran was involved in weapons research.

These so-called "alleged studies" included uranium conversion, high explosives testing and the adaptation of a ballistic missile cone to carry a nuclear warhead.

A US intelligence report in 2007 said Iran halted such research in 2003, but Mr Amano's report gives credence to the belief held by some western countries that the programme continued.

The information was "extensive... broadly consistent and credible in terms of the technical detail, the timeframe in which the activities were conducted and the people and organisations involved," the report said.

The 10-page document, which is to be discussed by IAEA governors at a meeting next month, also confirmed Tehran had begun enriching uranium to higher levels, theoretically bringing it closer to the levels needed for an atomic bomb.

Iran has previously reached uranium enrichment levels of no more than five per cent at its facility at Natanz, in defiance of UN orders for it to cease and despite three rounds of UN sanctions.

Earlier this month, Iran announced it would begin enriching uranium to 20 per cent, ostensibly to make the fuel for a research reactor that makes medical radioisotopes.

Iran insists its intentions are peaceful, but western powers suspect Tehran is enriching uranium to make nuclear weapons, as the material in high purity form can be used in the core of an atomic bomb.

The report said while the Islamic republic officially informed the IAEA of its intentions, it started feeding nuclear material into the uranium-enriching centrifuges before IAEA inspectors arrived in the plant to oversee the process.

The report said Iran had moved most of its stockpile of low-enriched uranium - 1,950 kilograms from an estimated total of 2,065 kilograms - for processing to higher levels.