They will have moved so close that sooner or later the ability and the opportunity to complete what they had started will present itself. From Israel's point of view and probably from the US point of view as well, the mullahs have to be seriously taken down a peg. and they need to be seen to be taken down a peg. Iran sponsors most of the terrorism in the world. They need to be defanged.
Firebomb thrown during demonstration in northern Israeli town of Umm al Fahm (Haaretz)
from the article: Sanctions alone won't stop Iran's nuclear work