Even massive bunker-buster bomb is no sure way to stop Iran if negotiations fail

If negotiations in Vienna to curb Iran's nuclear program fail, however, even an airstrike with the 30,000-pound Massive Ordnance Penetrator -- the largest non-nuclear bomb ever developed -- would delay Iran's nuclear efforts by only a few years, according to U.S. defense officials and private analysts. Israeli forces could do far less, these experts say.