"This is a case when the report really speaks for itself," State Department spokesman Sean McCormack said after the International Atomic Energy Agency (IAEA) accused Iran Monday of withholding details on alleged efforts to make nuclear weapons.

"It speaks to Iranian continuing refusal -- and I think I saw the phrase 'willful lack of cooperation' -- in answering these basic questions from the IAEA," McCormack told reporters.

The watchdog "is really acting on behalf of the international system in trying to dive into the history of Iranian research in developing nuclear weapons," he added.

"It is very troubling that the Iranian government refuses to answer questions about the military involvement in this program, which can raise a whole other set of issues about what were the activities vis-a-vis weaponizing or trying to weaponize a nuclear program," he said.

"So these questions remain unanswered. I think the report speaks for itself in that regard," he said.

Using far stronger language than the past, the IAEA on Monday expressed "serious concern" that Iran is still hiding information about alleged studies into making nuclear warheads and defying UN demands to suspend uranium enrichment.

The agency said it was "of the view that Iran may have additional information, in particular on high explosives testing and missile-related activities, which could shed more light on the nature of these alleged studies and which Iran should share" with the agency.

The alleged studies comprise a uranium conversion project, high explosives testing and designs for a missile re-entry vehicle, and suggest there may have been a possible military ang

le to past nuclear work.

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