The only viable option is sabotage....
Of the old-fashioned, delivered-by-shoe-leather kind...
In movie terms, this is a job for James Bond, not Maverick & Goose....
A PRE-EMPTIVE NUKE STRIKE IS NOT AN OPTION - it simply won't destroy the facilities in question, and will only piss off Iran even more. Since Israel does not have the ground/naval capabilities to actually invade Iran (it's call the Israeli DEFENSE force for a reason - they don't have the capability to operate a ground campaign outside their immediate region), the only other pre-emptive nuke scenario (as 'preparation' for a land attack) is out the window...
Remember: NUKES ARE POLITICAL BARGAINING CHIPS - once the shooting starts, we're back to conventional bombs & bullets - just like the Cold War....
Further, the IAF doesn't have the ability to destroy the program completely from the air... For that matter, the USAF may not be able to completely destroy it from the air...
The best option is for someone to "arrange" for the Iranians to have an "Accident" involving nuclear material, and maybe a Russian-made reactor or two (you never know with that shit, it's got a worse record than Glock...)...
Such an "Accident" would make it much more difficult for their nuclear program to be tolerated, especially if the fallout were to be distributed over the 'right' nations...
Like I said - cloak & dagger, not 'weapons free, fire at will'....