They wouldn t do it.
Simple as that.
In case they would, Israel would start it in a total act of panic (selfdefense)....
Because iranian foreign policy wants israel irradicated...
Israel has nukes.
Iran wants nukes.
USA will act pro israel, thats for sure.
China / russia will stop USA from acting though, since both sides know that any action of this sort would cause the destruction of the civilized world.
In case iran keeps acting up like that, i see a war with conventional weapons coming....~ 2-3 years max.
We ll see.
War = no winners