South Korea's rival political parties welcomed Friday the U.S. Congress' approval of a spending bill that calls on Japan to apologize for its sexual enslavement of Korean and other Asian women during World War II.

The Consolidated Appropriations Act for Fiscal Year 2014, which passed through the U.S. Senate on Thursday, is attached with a nonbinding clause calling on the secretary of state to step up efforts to get Japan to apologize for forcing as many as 200,000 women to provide sexual services for its troops during World War II.

U.S. President Barack Obama is expected to sign it into law on Friday.

"We greatly welcome the formal inclusion of the comfort women issue in U.S. federal law," Rep. Kim Gi-hyeon, the chief policymaker of South Korea's ruling Saenuri Party, said at a meeting of senior party officials.

"Comfort women" is a euphemistic term for the sex slaves.

"Japan should offer a sincere apology to the comfort women and bear proper legal and political responsibility," Kim said.

He also urged Japanese leaders, including Prime Minister Shinzo Abe, to refrain from words and acts that anger neighboring nations such as South Korea and China, both of which suffered from Japan's aggression in the early part of the 20th century.

Japan's relations with its nearest neighbors have soured further since Abe visited a controversial war shrine in Tokyo last month. The Yasukuni war shrine has been regarded by victims of Japan's aggression as a symbol of the country's past militarism.

South Korea's main opposition Democratic Party urged Tokyo to answer the call of the new bill.

"The passage of the bill serves as an opportunity for the whole world to remember that the comfort women issue is history that has yet to be resolved," Park Kwang-on, spokesman of the opposition party, said in a statement. (Yonhap News)