I suspect that Iran probably already has 2 or 3 bombs, and is waiting until they have ICBM’s built and 40-50 warheads to put in them, to announce that they are a nuclear power.
2 or 3 bombs aren’t a deterrent; they make you a target to a better equipped nuclear power that might be fearful enough to launch a crippling first strike.
2 would be an imminent threat to Tel Aviv.