For a long time, the US has treated Israel as an extension of American territory -- in essence, a US state. This proposal by the impending Obama administration -- which would treat an attack on Israel as an attack on the US, and would bring US nuclear retaliation against Iran -- is a dangerous escalation of the war party in the upcoming administration.
The reality is that the US is completely hypocritical about nuclear weapons. We have no intention of giving up our own weapons (and given US history of attacks using weapons of mass destruction, that should be an obvious first step) and we have no intention of asking Israel to give up their nuclear weapons, but the President-elect is by this action threatening the lives of millions of innocent Iranians. From Haaretz.com:
"U.S. President-elect Barack Obama's administration will offer Israel a "nuclear umbrella" against the threat of a nuclear attack by Iran, a well-placed American source said earlier this week. The source, who is close to the new administration, said the U.S. will declare that an attack on Israel by Tehran would result in a devastating U.S. nuclear response against Iran."