A similar situation is the more probable reading of current U.S. policy towards Iran. The United States wishes to deter Iran from building nuclear weapons. In order for deterrence to work, it is necessary to maintain a “credible threat” of something that you might do if the other side does that which you wish to prevent. In short, since the whole point of deterrence is to raise doubts in the mind of an adversary that a given course of action might be costly, it is necessary to demonstrate that you have the capability to carry out a threat of a military response.Of course, the flip side of that is that you have to give your adversary a credible second option. Iran has already seen what the U.S. policy is regarding simple denials, not to mention the actual nonexistence of nuclear weapons programs. Iraq was completely incapable of convincing the Bush administration that it had no WMD program. The failure of the UN inspectors to find evidence only convinced GWB that Iraq must be really effective at hiding their program and became the casus belli itself.
We've also declared that we won't speak with the Iranians, so they have no diplomatic out available.
Jason is right that the U.S. plans for wars it will never fight, we've undoubtedly got plans to fight the Russians and the Chinese (possibly even the French). But if senior U.S. officials were publicly claiming that we have no intentions of bombing Moscow, but we've been planning the attacks, would he think that was pragmatic deterrence or complete lunacy?