There are essentially two ways to negotiate. Option A involves taking extremely tough opening positions, doing lots of blustering, making frequent threats to walk away, and making concessions, if at all, only at the last minute. Option B, on the other hand, means identifying and mostly sticking to a reasonable opening position and minimizing posturing through the process.
I am reminded of this when I listen to the GOP candidates talk about foreign policy. While there are significant differences among the candidates on the wisdom of overseas military interventions, all of them seem to accept the default position that we need to increase our defense budget, remind both our friends and foes how great and powerful we are on a regular basis, and take extremely hard lines in negotiations, presumably backed by the threat of force in many cases.
Does Option A work better than Option B? It depends on the circumstances. If one is negotiating on a bilateral basis with a weak-willed opponent, quite possibly. If, on the other hand, one is trying to maintain the unity of a coalition of parties with substantially different interests, almost certainly not. Option A also increases the likelihood of failure and the risk that one might have to take undesired drastic action thereafter in order to maintain credibility with the other side and the world in general.
In the case of Iran, the notion that we could have held the international consensus together while using Option A is a fantasy.