Tokyo, Feb 14 : The Japanese government has effectively excluded its 20th century wartime atrocity against Koreans in a letter of formal recommendation for its former gold and silver mine to be included in the Unesco World Heritage List, informed sources said on Monday. Tokyo has launched a campaign to get the Sado mine designated as Unesco World Heritage Site next year despite Seoul's strong protest, reports Yonhap News Agency. As many as 2,000 Koreans were forced into hard labour at the mine during World War II, as their country was under brutal colonial rule by Japan. "(The Japanese government) recommended (the Sado mine) as having value of its mining technology and system from the 16th century till the mid-19th century," a Japanese government source told Yonhap. In the letter submitted to the Unesco on February 1, the official added, Japan placed a focus on the mine's activities during the Edo period (1603-1867), with the forced labour issue excluded in the core part, the official added. Japan used the name of "Sado island gold mines" in the document, instead of "the Sado complex of heritage mines, primarily gold mines" in its own preliminary list of heritage candidate sites in 2010, according to another source at the Foreign Ministry. /IANS