TOKYO (AP) — Osaka's outspoken mayor has said the system in which Asian women were forced to become wartime prostitutes before and during World War II was necessary to "maintain discipline" in the Japanese military.

Toru Hashimoto told reporters Monday that it was understandable that the so-called "comfort women" were needed to provide respite for Japanese soldiers who risked their lives in battle.

Hashimoto also is co-leader of the opposition Japan Restoration Party.

Historians say up to 200,000 women, mainly from the Korean Peninsula and China, were forced to provide sex for Japanese soldiers in military brothels. But some in Japan question whether the women were coerced by the military to be prostitutes.

Hashimoto's comments come amid concerns that Prime Minister Shinzo Abe wants to revise Japan's past apologies for wartime atrocities.