本文主要的論點是認為，美日安保條約自從冷戰結束以來，受到國內政治及經濟 因素影響越來越大，若單從國際體系層面及戰略因素已經無法管窺其轉變的原因與全貌。 本文以一九九六年四月，美日以「戰略模糊」策略修改安保條約「共同防衛合作指針」為例 ，認為日本將長久以來運用在經濟發展的「彈性規制」策略套用到安全政策上，為美日安保 條約的防衛政策增添許多彈性空間。 傳統的國際政治理論認為在國際合作的體制下，一旦外來的威脅不再存在，合作機制也將隨 之瓦解。以此論點印證在美日安保條約的架構上，我們認為長久以來美日之間的貿易衝突都 被戰略安全理由所掩蓋，一旦俄國的威脅消逝，貿易磨擦的聲浪便會超越安全合作，不平等 的夥伴關係即將宣告結束。但是就在一九九六年四月，美日兩國不但沒有因彼此的貿易磨擦 而中止其軍事聯盟，反而擴大其安保條約的防衛適用範圍，因此，本文嘗試以新自由制度主 義將安全與經濟議題做個連結，並以制度主義探討究竟美日安保條約隱含著甚麼樣的政經意 涵？及美國和日本之間存在著何種制度來調節兩國之間的關係。　

　　　　　The primary argument of this article is that the U.S.-Japan Security Alliance has been increasingly influenced by domestic politics and economic factors since the end of the cold war, which has lead to a weakening of the explanatory power of international strategic determinants. This article introduces Ronald Dore's concept of "flexible rigidities" to explain this transition of the U.S.-Japan Security Alliance. Traditional international political theory argues that a cooperative regime will break down with the disappearance of the common threat. Applying this theory to the U.S.-Japan Security Alliance, however, we find that both countries did not cease their security cooperation despite increasingly large trade deficits. Thus this article make use of new institutionalist arguments to link security and economic considerations between Japan and America.