BEIJING China said on Tuesday that Japan's agreeing to turn over sensitive nuclear material of potential use in bombs to the United States was a step in the right direction, but that it had other material it still needed to hand over.
The leaders of Japan and the United States, meeting at a nuclear security summit in the Netherlands, said that hundreds of kilograms (pounds) of material of potential use would be downgraded and disposed of.
"China welcomes the reaching of this deal," the Foreign Ministry said in a statement. "We appreciate and support the United States' hard efforts to collect sensitive nuclear materials from overseas."
China had voiced concern earlier this year about regional rival Japan's holding of plutonium, though Washington and the United Nations nuclear agency had made it clear they are not worried about the way Tokyo is handling the issue.
"Japan still stores a large amount of other sensitive nuclear material, which is still far in excess of our its own actual normal needs," China's Foreign Ministry added.
"We hope that Japan can further face up to the concern of the international community and keep taking earnest steps to resolve this serious imbalance of supply and need for nuclear materials as early as possible."
Japan, the world's only target of atomic bombs, during the final stages of World War Two, does not have nuclear weapons and has long said it will not seek to obtain them.
China, which has nuclear arms, is involved in a bitter territorial dispute with Japan over a group of uninhabited islands in the East China Sea.
It denies Japanese accusations that it is a threat to peace and in turn has accused Japan of trying to rearm and failing to learn the lessons of its brutal behavior during World War Two, when imperial Japanese forces occupied parts of China.
(Reporting by Ben Blanchard; Editing by Nick Macfie)