The issue of Asian women drafted as sex slaves for Japanese soldiers in World War II has been included in U.S. legislation for the first time in a bill passed by the House of Representatives on Wednesday.

An attachment to a spending bill for 2014 calls on the secretary of state to encourage the implementation of a 2007 resolution on the issue.

The House passed the spending bill for 2014 in a plenary session on Wednesday. The attachment notes the passage of House Resolution 121 and "urges the secretary of state to encourage the government of Japan to address the issues raised in the resolution."

The attachment is non-binding but has symbolic significance in pressuring Japan to apologize for the atrocities committed against sex slaves. The Senate plans to put the spending bill to a vote on Friday, and it apparently has a good chance of being passed.

U.S. Representative Mike Honda, a third-generation Japanese American, played a leading role in the passage of the 2007 resolution, which calls on the Japanese government to admit and formally apologize for the forced mobilization of women to serve as sex slaves for the Japanese Imperial Army.

Sources in Washington said the fact that the House of Representatives raised the issue again shows how strongly lawmakers feel about such abuses.

Sources added that the administration of Japanese Prime Minister Shinzo Abe, which has been bombarded with criticism from Korea and China since his visit to the militarist Yasukuni Shrine, "will find itself in an even more embarrassing situation."

But others caution against expecting a major shift in Washington's embrace of Japan as its key Asian ally. Many lawmakers probably did not know or care that the attachment on the sex slaves was included.