Simply a lie.
There WAS another option. That was to get Russia to stop building the damn nuke facilities.
Bush did nothing serious to stop Russia. Clinton did nothing to stop Russia. Don't let anybody say we ran out of options. We were just to wimpish to get Russia to stop the develpment and construction of Iran's capability.
Its not necessary to have nuke reactors (from the Russians)to build an atomic bomb. All that's needed is uranium ore (which Iran has natively) and the ability to enrich this ore, to the point of about 20%. U-235 is needed, and is rather a rare portion of all the uranium found, and when it is being enrivhed, it also needs to be seperated from the other isotopes of uranium. The russians didn't give the iranians this technology, it appears that A.Q. Khan did, and the euroweenies sold the iranians all the advanced hardware they needed to build the centrifuges, and other necessary items, such that the iranians now have a native ability to build all the centrifuges they need. The Iranians have had a nice cover, all along, thanks to the RUssians, though, as enriched uranium is necessary to fuel the reactor the RUssians are building for them. All along, Iran has maintained they are only building enrighment facilities for their reactors, when anyone with half a brain knows thats a lie. The russians have enabled them, to have plausible deniability, however. The russians are also helping them build heavy water plants, a necessary step, for the iranians to build plutonium weapons, which are many times more powerful than the atomic weapons the iranians are close to having. The atomic bombs the iranians are preparing t build will look like pop guns compared to plutonium weapons. One plutonium based weapon will totally make israel uninhabitable for centuries, whereas, it will take many atomic weapons to achieve the same effect. The real problem is that the knowledge is out there, to build nukes. Anyone with the resources and time, is capable of fielding a small atomic weapon, its a sad state of affairs we find ourselves in, and it will probably be very tumultuous in the coming decades, as non-state actors become capable of fielding advanced bio-weapons, as well as small nukes. Heck, the Iranians probably have enough uranium to currently build dozens of dirty nukes at this point, which are quite nasty little items, if smuggled into major cities and detonated.