LONDON, Feb. 20 The United Nations' top nuclear official says Iran has mastered technology that puts it six months away from enriching uranium on an industrial scale.In an interview with the Financial Times, Mohamed ElBaradei, director of the International Atomic Energy Agency, said Iran's centrifuges in Natanz would soon no longer be a pilot program and there was no turning back.You cannot bomb knowledge, he said. Enriched uranium can be used for nuclear weapons but also for nuclear power generation, which Iran claims is its only goal.He said Iran has a cascade of 164 centrifuges in the underground facility and experiments with two further 164-centrifuge cascades in the pilot program were functioning. ElBaradei was scheduled to meet with Iran's chief nuclear negotiator Ali Larijani in Tehran on Tuesday and said he doubted Iran would meet a Wednesday U.N. deadline to stop enrichment.U.S. and British intelligence estimates claim Iran is five to 10 years away from developing a nuclear bomb, the report said.Copyright 2007 by UPI