Katsuto Momii, the new head of Japan's NHK public broadcaster expressed "sincere remorse" on Tuesday amid the mounting criticism of his remarks about Japanese wartime atrocities.

As worldwide anger grows over several NHK executives' recent inflammatory comments on Japan's behavior during World War II, the new US ambassador to Japan, Caroline Kennedy, rejected an NHK interview request, Japan's Kyodo News Agency reported.

Japan's Mainichi Shimbun newspaper reported that Momii said at an NHK budget meeting held on Tuesday by the ruling Liberal Democratic Party: "I will be more cautious by understanding a situation before making a statement in the future.

"To eliminate the mistrust — which I am responsible for — I will work and fully engage my heart and soul."

Kennedy, the daughter of the US president John F. Kennedy, turned down the NHK interview request because of the "controversial remarks about wartime sex slavery made by the president of the company", Kyodo quoted sources close to the decision-making process as saying on Monday.

Tadamori Oshima, former deputy chief of the ruling party, told Momii that "mistrust is coming from inside and outside (NHK). It is the responsibility of the president to rebuild trust".

Momii made international headlines last month with his defense of the Japanese military forcing women in occupied countries into sexual slavery in the 1930s and '40s. When asked about "comfort women" at a news conference in late January, he said such institutions of sexual slavery existed in "every country" and that it is only considered wrong based on "today's morality".