The 1970s was an era of crisis and internationalization for Japan-U.S. relations. Both governments started to settle their bilateral conflicts for their policy cooperation which was required in the changing international environment at that time. To clarify the character of this change, this paper examines the bilateral negotiation of Tokai reprocessing plant held in 1977.<br>In the late 1970s, the U.S. government attempted to rebuild international nuclear nonproliferation system by limiting peaceful nuclear power development such as spent nuclear fuel reprocessing technology. Carter administration took the office in 1977 and called its allies to stop reprocessing. However, Carter's new policy was highly problematic since reprocessing was a key technology in energy policies of other developed countries such as Japan. As Tokai reprocessing plant was planned to begin operation in 1977 and an approval from Washington was required for its operation, they need a settlement.<br>At the first bilateral talk in April, Washington opposed firmly to the operation. On the other hand, international opposition grew rapidly against the new U.S. nuclear nonproliferation policy. Western European countries were especially sensitive to it since it could ban further export of nuclear-related technology to developing countries.<br>Washington started to consider a compromise since Tokyo was the only close ally showing its approval to a framework of new nonproliferation policy. At the second meeting, the United States offered a proposal to alter Tokai plant more resistant to nuclear proliferation by technical modification. Although Japanese government opposed to the modification, they agreed to do a research about possible technical alternatives at Tokai Mura, Japan. As a result of this joint research and other investigations, however, Washington gave up all the technical solutions. Finally, at the third meeting at the end of August, Carter decided to permit the operation without any modification in return of Tokyo's agreement to reconsider reprocessing and suspend large scale Plutonium use for the moment.<br>The above examination shows two aspects of the Japan-U.S. relations in the1970s. One is that Tokyo had an option to refine the U.S. foreign policy and participate in international politics by supporting Washington. In contrast to European countries that stopped the U.S. nonproliferation policy by refusing to cooperate, Japan did the same thing by aligning with the United States.<br>The other is decreased importance of the bilateral relationship itself for the U.S. government, while Japan's substantive contribution to the U.S. foreign policy became a must to the United States. In sum, although both countries agreed to coordinate their policy objectives in the 1970s, this success became a basis of further bilateral conflicts on the way of implementing those goals.