This article explores the potential impact of U.S. disarmament leadership on the nuclear diplomacy of North Korea and Iran, the "defiant states." The first part of the article introduces the concept of "interaction capacity," which measures a state's integration into international society, based on its physical communication systems and its adoption of shared norms. The theory predicts that lower levels of interaction capacity will generate a greater propensity for nuclear defiance, as the affected states reject and try to resist integration pressures. In the second and third parts of the article, this conceptual framework is applied to the cases of North Korea and Iran. The analysis suggests that efforts to reassert U.S. disarmament leadership could increase the alienation of North Korea and Iran, leading to provocation and escalation of nuclear tensions. The final part of the paper explores the policy implications of this analysis for the potentially defunct six-party talks, for hopes of renewed negotiations with Iran, and for the 2010 Review Conference of the Treaty on the Non-Proliferation of Nuclear Weapons.