Should the U.S. Place Israel Under the Umbrella?

According to Fox News, President-elect Obama is readying a "strategic pact" that would place Israel under the U.S. nuclear umbrella.

I don't quite understand why this is necessary. As I understand it, the "nuclear umbrella" concept was anchored to a very clear strategic rationale during the Cold War. America was endangered by Soviet expansionism but couldn't station conventional forces everywhere. Simultaneously, the U.S. wanted to keep the number of nuclear nations low.

None of these dynamics are at play in the Middle East.

Israel has nuclear weapons. As I wrote in RCP earlier, if Iran is undeterrable, they're undeterrable whether it's American or Israeli bombs falling on Tehran. If they are deterrable, then Israel's nuclear arsenal of some 200 bombs deliverable by land, sea and air, should be amply sufficient.

As for proliferation, a strategic pact for Israel alone is worthless, unless we make a similar offer to every Arab state in the region (as Hillary Clinton acknowledged). I also don't see the strategic value. Iran is not poised to march on Tel Aviv, much less acquire any territory beyond its borders. Iran can be dangerous, but it's not powerful.

All this "strategic pact" would do is restrict U.S. options in the event of a crisis.

So why make the offer? Is there something I'm missing?