During a recent town meeting in Shizuoka, Nakayama had said, "The term 'comfort women' has not always existed."
"I apologize for causing trouble," Nakayama told Chief Cabinet Secretary Hiroyuki Hosoda in the Diet Building Tuesday morning, the Mainichi Shimbun reported.
"I'd like you to consider the diplomatic repercussions of your remarks when you speak," Hosoda warned Nakayama.
Shortly after the town meeting, Nakayama explained that he meant the term "comfort women" is relatively new and that he was aware that a massive number of women were forced to have sex with Japanese soldiers during World War II.
Among the comfort women, "there were many Japanese people and many people from the Korean Peninsula. I know they can't even find words to describe the hardships they experienced," Nakayama said. "I meant that there was no such term, even though I know (sex slaves) existed," he added.