Preemptive strike on Iran would only be counterproductive
With regard to Iran, there is no reason to believe that an attack on the facilities in Bushehr, Arak, or Natanz would have any different consequence than the Osirak example. Such an attack would likely embolden and enhance Iran's nuclear prospects in the long term. In the absence of an Iranian nuclear weapon program, which IAEA inspectors have yet to find, a preemptive attack by the United States or Israel would provide Iran with the impetus and justification to pursue a full blown covert nuclear deterrent program, without the inconvenience of IAEA inspections. Such an attack would likely be seen as an act of aggression not only by Iran but most of the international community, and only serve to weaken any diplomatic coalition currently available against Iran.The most troubling aspect of such a scenario is that, unlike Iraq in 1981, Iran is not dependent on foreign imports for nuclear technology and already has available the raw materials, and most of the designs and techniques, required to pursue a nuclear weapons program. Iran has the necessary know-how and has already produced every stage of the nuclear fuel cycle. Furthermore, Iran has uranium mines in Yazd and is in the process of constructing milling plants to manufacture yellow cake uranium and conversion plants that convert it to UF6 gas. Iran has also begun manufacturing its own gas centrifuges used to enrich uranium. Even if Natanz, Arak, and Bushehr were destroyed in a preemptive strike, Iran probably has duplicate equipment that can be activated and has the know-how to produce more, to pursue a more vigorous and unabated nuclear weapons program in the long term.
An attack on Iran's nuclear facilities could have the preverse effect of increasing their timetable for developing nuclear weapons. Assuming that the military strikes do not destroy all of Iran's facilities and their nuclear supplies, Iran will be able to overtly embark on a crash course towards nuclear weapons with more international support.