BEIJING -?A Chinese Foreign Ministry spokesman said on Friday that China still wants Japan to explain its nuclear stockpile to the world.

Spokesman Qin Gang was commenting on media reports that Japan will comply with a US request to return plutonium provided for research during the Cold War, but refuses to clarify the issue of highly enriched and weapons-grade uranium.

Qin said that highly enriched and weapons-grade uranium, as well as plutonium are sensitive nuclear materials. Any supply-demand imbalance of such sensitive materials is a nuclear security and proliferation risk.

China maintains that the Japanese government should answer the question of how much uranium of concern there is in Japan, the government should then explain the use and supply-demand situation.

"We continue to urge the Japanese government to take a responsible attitude and explain itself to international community," Qin said.