The head of the Upper House has sent a letter to her South Korean counterpart asking him to retract comments urging the emperor to make an apology regarding the issue of the "comfort women," sources familiar with the matter said Thursday.

As there was no reply from National Assembly Speaker Moon Hee-sang, House of Councilors President Akiko Santo decided not to arrange one-on-one talks with him on the sidelines of a multilateral meeting next week, the sources said.

The term "comfort women" is a euphemism used to refer to women who provided sex, including those who did so against their will, for Japanese troops before and during World War II.