Iran may be withholding information needed to establish whether it tried to make nuclear arms, the International Atomic Energy Agency (IAEA) said on Monday in an unusually strongly worded report. The tone of the language suggesting that Tehran continues to stonewall the IAEA revealed a glimpse of the frustration felt by agency investigators stymied in their attempts to gain full answers to suspicious aspects of Iran's past nuclear activities. A senior U.N. official familiar with the agency investigation into Iran's nuclear programme said none of the dozens of agency reports issued in that context had ever been as plain spoken in calling Tehran to task for not being forthright. Iran has described its cooperation with IAEA probe of its alleged nuclear weapons experiments as positive, suggesting it was providing information requested by agency officials. Ali Ashgar Soltanieh, Iran's chief delegate to the IAEA said as much again on Monday, that the report described "the peaceful nature of our nuclear actions.' "The Americans failed ... in shameful attempts' to co-opt the agency into delivering anti-Iranian findings, he added, highlighting a paragraph in the report saying that agency experts have been given access to all declared nuclear material in the country and verified that all of it was accounted for. But Gregory L. Schulte, his U.S. counterpart, suggested the report was a strong indictment of Iran's defiance of the international community's efforts to seek answers about troubling parts of its nuclear program, noting it "details a long list of questions that Iran has failed to answer.' "At the same time that Iran was stonewalling its inspectors, it's moving forward in developing its enrichment capability in violation of Security Council resolutions,' said Mr. Schulte. He described parts of the report as a "direct rebuttal' of Iranian claims that all nuclear questions had been answered. U.S. intelligence said Iran stopped work on nuclear weapons in 2003 but some other nations believe such activities continued past that date. The report noted that Iran continued to deny such allegations. The restricted report forwarded to the U.N. Security Council and to the 35 board members of the IAEA also noted that Iran remained defiant of U.N. Security Council demands to stop uranium enrichment. Shrugging off three sets of council sanctions, Iran had instead expanded its operational centrifuges