We know Iranians are in Syria and Lebanon. They are Iran's forward positions. Cripple or destroy as they would be the first to retaliate in such an attack upon Iran. Yes, don't tell US all the plans. We have leaks in our intel groups. Nobody is more threatened by Iran than Israel. US is more afraid of world oppinion than over Iran. You will be on your own, but heck, we will get part of the blame anyway.
U.S. to defend Syrian rebels with airpower, including from Assad (Reuters)
from the article: Think tank: Israel could attack Iran's nuclear program alone