Australia, New Zealand, and Japan were among the closest allies of the United States during most of the Cold War period. The three Pacific allies were also among the leading advocates of nuclear disarmament. These countries often found themselves in a conundrum between a nuclear alliance and nuclear disarmament. While the United States constantly pressured its allies into line with the solid Western position in the Cold War struggle, especially regarding nuclear policy, their domestic actors repeatedly challenged the nuclear alliance with the United States and urged their respective governments to adopt stricter non-nuclear policies and an activist nuclear disarmament policy.<br>This article analyzes this “dilemma” among the three allies between their nuclear disarmament and non-nuclear policies, on the one hand, and their alliance with the United States, on the other. The article explores how their successive governments sought to resolve this dilemma and how such efforts affected their alliance with the United States. There were two significant attempts by them to resolve the dilemma during the Cold War, one by New Zealand's Lange government in the mid 1980s to persuade the United States into “de-nuclearizing” their alliance and the other by Australia's Hawke government in the early to mid 1980s to win over its domestic anti-nuclear critics by pursuing an activist nuclear disarmament diplomacy. Both had mixed results in terms of making alliance and nuclear disarmament compatible. New Zealand virtually had to leave the U.S. alliance while Australia had to compromise its non-nuclear policies.<br>After the end of the Cold War, New Zealand and Australia developed two contrasting approaches to nuclear disarmament which were based on their critical choices made about the U.S. alliance. New Zealand, leaving the “nuclear and security umbrella” of the United States, sought to pressure, with other disarmament-oriented countries, its former ally and other nuclear powers into accepting nuclear disarmament in the changed strategic environment of the post-Cold War world. Australia, along with Japan, which began to pursue a more activist nuclear disarmament policy, sought to overcome the alliance-disarmament dilemma by influencing U.S. nuclear disarmament policy from within an alliance framework.<br>In the final section, the article gives some assessment of the effect of the Obama administration's nuclear policy on this alliance-nuclear disarmament dilemma. It ends with a tentative conclusion that the Obama administration, with its unprecedented pursuit of nuclear abolition as a concrete U.S. policy objective, has drastically changed the global dynamic of nuclear disarmament politics and has a potential to greatly affect the historical alliance-nuclear disarmament dilemma for Japan, Australia and other disarmament-minded U.S. allies.