The evolving strategic competition in South Asia poses an unprecedented challenge for U.S. policymakers who believe that "open-ended nuclear weapon and missile programs in India and Pakistan threaten regional and international security and increase the risk of onward proliferation from the region". Today, India and Pakistan are racing to modernize, expand, and operationalize their nuclear deterrent capabilities. Several decades of international nonproliferation measures helped to delay, but not prevent, their testing and overt production of nuclear weapons and ballistic missiles. In the past, the United States learned how to deal with both allies (the United Kingdom and France) and adversaries (the Soviet Union and China) that went through a similar stage of nuclear force modernization. But coping with the nuclear maturation of nations with which Washington has neither a formal alliance nor any real adversity is a novel undertaking for which the U.S. government does not yet have a coherent, long-term policy. Should the United States try to help, hinder, or not involve itself with the modernization and expansion of nuclear deterrent arsenals in South Asia? This article examines the current policy challenges for the United States in dealing with the India-Pakistan nuclear rivalry.