How are we as a world going to prevent the crisis building in Iran?

Iran has already said it will nuke Israel once it has the weapons..Obviously Israel is not going to allow that and they will strike first..Syria,Libya, Egypt will retaliate against Israel..Possibly Russia too..The US will protect Israel and all hell will break loose..Most of NATO will join the US and Pakistan will join their Muslim brothers..A big mess just because Iran has some whacko leader