The United States said Tuesday Iran's refusal to answer questions from the International Atomic Energy Agency (IAEA) on its nuclear program is "very troubling".

"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," State Department spokesman Sean McCormack said.

McCormack said this showed Iran's "willful lack of cooperation" with the IAEA.

"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 said.

According to media reports, an IAEA report said Monday Iran continues to defy demands to suspend uranium enrichment and has yet to disprove allegations that it is pursuing nuclear power for military use. However, Iran insisted that it has answered all questions from the IAEA.

The United States has accused Iran of trying to develop nuclear weapons under the cover of a civilian nuclear program. Iran has denied US charges and insisted that its nuclear program is for peaceful purposes only.

(Xinhua News Agency May 28, 2008)