Considering Iran has been under one form of sanction or another for the last 30 years the end result, I would think, should be some sort of change in international policy towards them. I believe further sanctions are likely, but those can only be effective with Russia and China fully on board.
With regards to war, the US alone does not have the capability to mount effective military action against yet another country, nor do I believe its people have a will to do so without clear provocation. Tactical strikes to cripple Iranian nuclear capabilities are possible but would likely be ineffective in the long term and possibly redouble their resolve without a wholesale change in Iranian leadership.
Without a much greater understanding of Iran I can’t really give much more of an answer, but it seems that their goal is more of proving to the world their legitimacy and power, less of becoming some evil, nuclear powered, monster. Personally I think there must be a way to let them have their pride while removing any real threat of nuclear proliferation.