Since the U.S. took a very different position against the Iranian and Pakistani nuclear programs; between 2005 and 2010, this paper attempts to establish what originated that difference in position. For this, the constructivist theory of Alexander Wendt best exemplifies how the performance of actors in front of others depends on the perception they have of each other . To this extent, this paper seeks to know what factors explain the difference of perceptions that the U.S. has of Iran and Pakistan meet its nuclear programs between 2005 and 2010. The factors identified and explained in this paper are: the historical relations of the U.S. with Pakistan and Iran, the political compatibility level of these countries, and the position of Iran and Pakistan on the issues of U.S. security.
