Two Israeli air force squadrons are training to blow up an Iranian facility using low-yield nuclear “bunker-busters”, according to several Israeli military sources.
The attack would be the first with nuclear weapons since 1945, when the United States dropped atomic bombs on Hiroshima and Nagasaki. The Israeli weapons would each have a force equivalent to one-fifteenth of the Hiroshima bomb.
Under the plans, conventional laser-guided bombs would open “tunnels” into the targets. “Mini-nukes” would then immediately be fired into a plant at Natanz, exploding deep underground to reduce the risk of radioactive fallout.
There is always the question of how seriously such saber rattling should be taken, but once such threats are on the table, it's awfully hard to make them disappear.
I also suspect that it would be very hard to actually "reduce the risk of radioactive fallout" by very much. Since the targets would include lots of uranium, it seems likely that a whole lot of very radioactive material would be injected into the atmosphere, quite possibly poisoning large chunks of Asia. If it's actually possible to open tunnels into the nuclear facilities with conventional bombs, why bother with nukes, since a couble of conventional bombs would very efficiently smash up anything inside. If tunnels are open, there is already a vent to the atmosphere - and an underground burst is the most efficient way to create a large amount of highly radioactive nuclear fallout.
If I were the leader of Pakistan, India, or China, I would quietly inform Israel that any unprovoked nuclear attack on Iran that poisoned citizens of my country would be treated as a nuclear attack on my country.
I suspect that the real motivation of Israel here (assuming this leak is for real) is to push Bush into attacking Iran. He is definitely dumb enough to do it.