HONOLULU - Iran must respond soon to a report by the U.N. atomic agency alleging that it is working secretly on developing a nuclear weapon, U.S. Secretary of State Hillary Clinton said Friday while attending a Pacific Rim summit.

Clinton said she discussed the issue with her counterparts gathered in Hawaii who also expressed serious concern over the issue.

"Iran has a long history of deception and denial regarding its nuclear program and in the coming days we expect Iran to answer the serious questions raised by this report," Clinton told reporters.

"The U.S. will continue to consult closely with our allies on the next steps we can take to increase pressure on Iran," Clinton said.

The International Atomic Energy Agency showed satellite images, letters and diagrams to 35 nations earlier Friday in Vienna as it sought to underpin its case that Iran apparently is working secretly on developing a nuclear weapon.

Iran's chief envoy to the IAEA, however, rejected the presentation as based on material fabricated by the United States and its allies.

The IAEA report strongly suggested that Iran is using the cover of a peaceful nuclear program to produce atomic weaponry.

Iran is under U.N. sanctions for refusing to stop uranium enrichment -- which can produce both nuclear fuel and fissile warhead material -- and other suspected activities that the international community fears could be used to make atomic arms. It dismisses such allegations and says its activities are meant to be used only for energy or research.