Japanese occupation troops left behind hundreds of thousands of chemical weapons at the end of World War II, and Tokyo is responsible for their cleanup under a 1997 treaty.
China says thousands of Chinese have been killed or hurt since the end of the war in 1945 from accidents related to the buried weapons.
China's ministry of defence said today that because they were widely scattered, the remaining pieces of Japanese chemical weapons were difficult to find and destroy. The ministry urged Japan to "increase manpower and resources" to finish the job under the conditions of the international convention.