Iran's nuclear weapons program is fairly well distributed over numerous locations. Whoever attacks it will have to attack many difficult targets.
We keep hoping Israel will do it because we know that their leadership is serious, and united enough to launch an attack like this, and stick together through all of the counter-attacks and international outcry that would surely follow.
We hope this because we fear that we are not sufficiently united to accomplish this same attack. We know that we are the best suited, in terms of equipment and basing; this is precisely the kind of attack our forces are designed for. But we know that we are not united enough to carry this out. The president who ordered it would risk impeachment, the party that supported it would be pounded in the press, at the UN, on every campus. Few politicians are prepared to take that kind of political risk.
And so we hope Israel will do it. But they don't have the reach to take out 80 hardened targets 2000 kilometers from home. We do.