Japanese chief cabinet secretary Yoshihide Suga says the government is in talks with the US over the return of a plutonium stockpile which was provided by the Americans during the Cold War.

The Japan Times cited government sources, saying the two sides aim to work out the details by the third nuclear security summit, scheduled for the end of March. The stockpile is more than 300 kilograms of mostly weapon-grade plutonium.

The Obama administration has been seeking return of the plutonium as part of a drive to strengthen nuclear security. But Tokyo initially resisted, citing the need to research fast reactors.