Japan's push to establish a nuclear fuel recycling program and use the plutonium created in the process was the center of an intense debate in the U.S. government four decades ago, pitting those who wanted smooth relations with Tokyo against those who worried the plan might lead to the proliferation of sensitive nuclear technology and plutonium stockpiles.

Formerly classified U.S. State Department and National Security Council memos and cables posted Thursday show that Tokyo began pressing Washington in the late 1970s to let it reprocess spent nuclear fuel from U.S. reactors so the extracted plutonium could be used in the so-called fast breeder reactors Japan wanted to build.

The documents were made available by the nongovernmental Washington-based National Security Archive at George Washington University and the Nuclear Nonproliferation International History project at the Woodrow Wilson International Center for Scholars.