The head of the International Atomic Energy Agency cautioned Thursday an attack on Iran over its refusal to freeze programs that could make nuclear weapons would be "an act of madness," in indirect warnings to the United States and Israel. IAEA chief Mohamed ElBaradei also said Iran could be running close to 3,000 uranium-enriching centrifuges by the end of next month - a number agency officials have described as the point of no return in the start of a large-scale program. ElBaradei spoke at the end of a meeting of his agency's 35-nation board, a gathering that focused on Iran's refusal to heed UN Security Council demands that it freeze activities that could serve to make nuclear arms and provide long-sought answers on suspicious aspects of its nuclear program. He also urged Iran to offer a "self-imposed moratorium" on enrichment, describing it as a "good confidence-building measure" that could launch negotiations on the standoff But the chief Iranian envoy to the meeting asserted his country would never suspend enrichment - the key issue of Security Council concern. Even while calling for a negotiated solution, both the United States and Israel - which has been threatened with extermination by Teheran - have refused to dismiss outright the possibility that they might target Iran militarily if it refuses to back down on enrichment and other areas of concern. But ElBaradei described any use of force as "an act of madness ... (that) would not resolve the issue." "The next few months will be crucial," he said, adding: "Iran is building a capacity, a knowledge" of enrichment that is irreversible, while not providing "an assurance that this is a peaceful program." "Even if Iran wants to have a weapon they are three to eight years away," giving ample time for both sides to move from confrontation, ElBaradei said, citing unnamed intelligence sources for his estimate. But, "the longer we delay, the less option we have to reach a peaceful solution," he added. Iran's defiance of UN Security Council demands to mothball both enrichment and construction of a plutonium-producing reactor as well as to increase cooperation with IAEA inspectors trying to shed light on activities that could be used to make weapons have led to two sets of sanctions. And a recent IAEA report prepared for the board meeting confirmed that Iran was expanding its activities and continuing to stonewall the IAEA in its attempts to gain more information on past activities of concern. That set the stage for a new round of Security Council-imposed penalties. Declaring Thursday that Teheran had become the "master of uranium enrichment" Ali Ashgar Soltanieh, Iran's chief IAEA envoy, said his country will never suspend its program. Like enriched uranium, plutonium can be used for the fissile core of nuclear warheads. Iran denies such aims. It says it wants to develop enrichment to generate nuclear power and asserts it is building the Arak reactor for research and medical purposes and not for its plutonium capabilities. Soltanieh evaded a question on whether his country had solved all technical problems in the intensely complicated enrichment process of spinning uranium gas through centrifuges at high speed. US officials, discussing confidential matters on condition of anonymity, have told the AP their information indicates Iran has not yet achieved technical perfection in enrichment. And on Thursday, Gregory L. Schulte, the US envoy to the IAEA, scoffed at Soltanieh's claim of enrichment mastery, telling Associated Press Television News: "The Iranian ambassador spins faster than any centrifuge." ElBaradei, however, cautioned that Iran was "speeding up its enrichment capacity" to the point where it could have just under 3,000 running in series by the end of July and "was steadily moving toward perfecting the technology." "Whether some of the centrifuges are running with the speed desired whether some of the centrifuges have been crashed, that is a part we have yet not seen and we still have to do some analysis," said ElBaradei. "But it is clear according ... that they are meeting their expectations at least in terms of the level of enrichment," he said, alluding to his agency's recent confirmation that centrifuges at Teheran's underground Natanz facility have churned out small amounts of fuel-grade enriched uranium. IAEA officials have informally identified an Iranian enrichment operation running 3,000 centrifuges as the start of a large-scale program, while experts say that number could produce enough material for several warheads a year. Teheran says it wants to operate 54,000 centrifuges - enough for a full-scale weapons program should it want to go that route. ElBaradei urged Iran not only to freeze enrichment and construction of its plutonium-producing reactor but also to end its stonewalling on past nuclear work that could be linked to a weapons program. The IAEA needs Iran's nuclear history, "not for the history's sake but to make sure that today, all nuclear activity in Iran ... is exclusively for peaceful purposes," he said.