The Center for Research and Documentation on Japan's War Responsibility and two other Japanese support groups compiled and submitted a joint proposal to the government, calling it to acknowledge that the sex slavery were against the victims' wills and to offer a formal apology.

The U.S. House of Representatives on Monday unanimously passed a bill which demanded the Japanese government to acknowledge formally and accept responsibility for the sexual exploitation of "comfort women" by the Japanese military during World War II.

Japanese Prime Minister Shinzo Abe said Tuesday that the passage of the resolution was "regrettable". When asked if Japan would make a formal apology to the victims, Abe avoided a direct answer, only saying, "the 20th century was an era during which human rights were violated. What is important is to make the 21st century a bright one for the world where there will be no human rights violations."

The Japanese government maintains that it has been sticking to a 1993 statement made by the then Chief Cabinet Secretary Yohei Kono, who officially acknowledged and apologized over the fact that Japan forced women from other Asian countries to be sex slaves for its soldiers during World War II.

However, Tom Lantos, chairman of the Foreign Affairs Committee, U.S. House of Representatives criticized Monday that Japan has been continuously promoting "historical amnesia" over the issue.

Besides the joint proposal from support groups, the Japan Action Network for the Military Sexual Slavery Issue, which consists of some 20 civic groups and individual members, also issued a statement on Tuesday calling on the government to respect and implement the U.S. resolution.

The US resolution also urges the Japanese Prime Minister to make a public apology, calling on the Japanese government to refute any claims that the episode never happened and wanting future generations to be told of "this horrible crime."

An estimated 200,000 women were forced to serve as sex slaves, known as "comfort women," for Japanese forces during World War II, and most of them came from countries invaded by Japan at that time.