The purpose of this paper is to develop a greater understanding for US perceptions of Common European Security and Defence policy (CESDP) by looking at major factors, interests, threats, and opportunities that seem to influence thevarying degrees of US support. The first chapter of this paper gives a short historical overview of European security and defence issues and examines the current process of developing CESDP. The second chapter focuses on US strategic interests in Europe and the compatibility of American and European interests. The third chapter presents both opportunities and threats that European security and defence reforms could pose to the transatlantic security partnership. The final chapter looks at possible outcomes of CESDP and discusses ways to ensure a lasting transatlantic partnership on security and defence.