Iran learned the lesson of Iraq and has buried its nuclear assets deep. It would take a weapon like a B61-11 to take them out. If Israel has such a nuclear weapon, they could take out Iran's nuclear program. But short of using nukes, no one, not even the USA has a conventional weapon that can take out deep underground bunkers.
You also have the distance problem. Israel if it used planes would have to refuel them to complete the mission and would also have to fly over some other nation such as Syria, Jordan, etc. I doubt those nations would be OK with that. Israel could use its Dolphin subs. It has three right now with two more due to arrive in 2010. Those have nuclear cruise missile capability and they could be used to take out at least the surface structures and shafts leading to the underground bunkers but again, without a specific weapon designed to take out deep bunkers, Israel at best could only hope to slow down Iran.
Bottom line, it is going to take nukes to stop Iran from getting nukes. Talk is not going to do it, sanctions are not going to do it.