Deterrence at present is not the most effective way in preventing Iran from developing nuclear weapons

For deterrence to work, it must be credible. It is here that the problem lies. This post shall discuss the extent to which the deterrence at present is credible and therefore effective. It will become evident that the US threats are not entirely credible and therefore deterrence may not work in achieving the US aim of preventing Iran from developing nuclear weapons. The threats the US has made include the assertion that if Iran creates weapons, it would face serious punishment (war or a nuclear strike). Another assertion which was famously made by Hillary Clinton in 2008 in a report for ABC News was that if Iran attacks Israel the US will obliterate Iran. 

Zagare and Kilgour as well as other political scientists have made credibility synonymous to rationality. Their point is that if a threat is rational then it is credible. The rationality of the US threats can be questioned. Following the same line of thought of de Gaulle who once rhetorically asked the question- would the US risk New York and Washington for Bonn and Paris?- I would like to ask the question of whether the US would risk New York and Washington for Tel Aviv or Jerusalem? from this question the true risk of the threat for the US is exposed and the threat seems less rational altogether. On this point of rationality, a military strike on Iran may pose too much of a risk- indeed- bombing Iran can create a chain reaction of attacks against the US or European institutions alike. This route of action therefore becomes irrational for the gains will be minimal in comparison to the losses, especially if one takes into consideration the shock which will be experienced by the international system. 

On a different note, the US track record in North Korea lessens the credibility of their threats to Iran. Indeed,  the US had threatened North Korea numerous times and had declared that it would not accept a nuclear armed North Korea. Despite the numerous threats, the US failed in taking action accordingly and in containing the North Korean nuclear program and they managed to proceed with nuclear armament and develop nuclear weapons. Thereafter the US had to change strategies and tried to apply concessions on their nuclear weapons. Moreover, to Obamas threats made about the US continued commitment to extend "deterrence  to Seoul, including the US nuclear Umbrella" North Korea responded that they now had more of a reason to create further weapons. What this case demonstrates is that US threats are not credible because they are not carried out, and that North Korea does not obey US commands. 

To conclude, the only credibility the US holds in its threats is that they have the military power to carry out their threats. However, assuming that the US is a rational actor and if one takes the case of North Korea into consideration, it doesn't seem like the threats can be described as credible, and therefore may not prevent Iran from developing nuclear weapons. Thus, the US, in order to be effective, it must increase its credibility by henceforth making rational threats and acting out on their threats. Additionally the US needs to make a costly signal.