"America has no truer friend than Japan, and there is no more important place I could serve my country than in Japan," Kennedy told The Yomiuri Shimbun.
Kennedy arrived in Japan Nov. 15 with a list of issues to deal with, including the relocation of the U.S. Marine Corps' station in the Okinawa Prefecture.
Although the move was approved by both governments, the prefecture has objected to the decision.
Kennedy said the new location was the best choice.
"I look forward to visiting Okinawa soon," she said. "We hope that substantive progress is made in the near future."
She also said she hopes Japan will play a more active role in international affairs -- and that the relations between Japan, South Korea and China will improve.
"Of course, the United States welcomes Japan's working more closely with us and with others in the international community to address common challenges and threats," she said. "A Japan that can more easily participate in international peacekeeping operations, for example, is in everyone's interest."