The USA is not afraid Israel will attack Iran, they want them to attack. That way Israel can help save face for America, accomplish the destruction of the nuclear facilities, and keep another war from being blamed on Bush. Israel will attack, but after their last pathetic performance in Lebanon they better be careful!
Defense Ministry says had no knowledge of alleged improper defense deals by Gal Hirsch (Haaretz)
from the article: Report: Washington concerned Israel gearing up to attack Iran