Israel is a client state of the US. If the US forbids an attack on Iran then Israel is unlikely to disobey their master. The chaos that Iran could unleash against the US in Iraq means that Bush is merely blowing hot air (again).
U.S. to deliver 8 advanced F-16s to Egypt on July 30-31, U.S. embassy in Cairo says (Reuters)
from the article: Report: Washington concerned Israel gearing up to attack Iran