Here's the thing. Everyone knows Israel has nuclear weapons. They openly threaten the "Samson Option" to destroy enemies or the whole world if they are threatened. One of their less-successful prime ministers even said it openly.
"Iran openly, explicitly and publicly threatens to wipe Israel off the map. Can you say that this is the same level, when they are aspiring to have nuclear weapons as America, France, Israel, Russia?" --Israeli Prime Minister Ehud Olmert
And, here's the real kicker, under US law, the US would have to suspend aid to Israel were it found that Israel has a 'roque' nuclear weapons program. That's the non-proliferation policy of the United States.
Thus leading to this rather funny video of watching many high ranking Americans go to great lengths not to be caught on video acknowledging that Israel has nuclear weapons.