BEIJING, Jan. 16 -- China will work with the Republic of Korea (ROK) in urging Japan to understand and reflect on history, Foreign Ministry spokesman Hong Lei said on Thursday.

Hong's comment came in response to an ROK plan to apply to register records on Japan's wartime sex slaves with UNESCO.

Forcing women into sexual slavery was a grave crime against humanity by the Japanese military during WWII, causing suffering in China, the ROK and southeast Asian countries, Hong said.

China and the ROK have similar experiences and concerns on historical issues relating to Japan, Hong said.

"China is willing to work with other victim countries, including the ROK, to maintain historical justice," Hong said, adding that Japan should work to gain the trust of its neighbors and the international community through concrete action.

The U.S. House of Representatives on Wednesday passed a bill calling for Secretary of State John Kerry to encourage Japan to address the issue of "comfort women", the contemporary euphemism for sex slaves.

The resolution calls for Japan to "formally acknowledge, apologize and accept historical responsibility in a clear and unequivocal manner".

Historians estimate that 200,000 women were forced into sexual servitude by Japanese forces during WWII, most from countries invaded by Japan at the time.