TOKYO -- The Japanese government is urging the country's power companies to work together to reduce their plutonium stockpiles in response to American requests, though logistical hurdles remain.

Tokyo told the Federation of Electric Power Companies of Japan that big power providers should cut back their supplies. A possible first step would be to use the mounting stockpiles of plutonium at Tokyo Electric Power Co. Holdings and Chubu Electric Power in reactors operated by Shikoku Electric Power and Kyushu Electric Power.

Japan's power companies take plutonium extracted through reprocessing spent nuclear fuel and turn it into mixed oxide fuel, or MOX, for reuse in their nuclear power plants. But with so many reactors still offline in the aftermath of the 2011 nuclear meltdown at Fukushima, plutonium stockpiles are only growing.

Given that the material can potentially be used to produce nuclear weapons, and amid efforts to convince North Korea to give up its nuclear program, the U.S. is urging Japan to reduce its stockpiles as well.

But this will be no easy task. Power companies so far have only ever used plutonium from their own facilities, given the potential consequences should fuel from elsewhere cause an accident. Local governments and residents are likely to resist any attempts to bring more nuclear fuel into their backyards.

Power providers acknowledge the difficulty of reducing their stockpiles by consuming plutonium on their own. "The companies must work together on issues that affect nuclear power as a whole," a government official said. The public and private sectors will need to coordinate efforts on the issue as well.