According to The Guardian (UK Newspaper)
Israel asked US for green light to bomb nuclear sites in Iran
Source
The then prime minister, Ehud Olmert, used the occasion of Bush's trip to Israel for the 60th anniversary of the state's founding to raise the issue in a one-on-one meeting on May 14, the sources said. "He took it [the refusal of a US green light] as where they were at the moment, and that the US position was unlikely to change as long as Bush was in office", they added.