Japan should step up intelligence sharing and military exercises with the United States as part of the bilateral alliance against possible contingencies over Taiwan and North Korea, according to a former Biden Senate aide.

Frank Jannuzi, now president of the Maureen and Mike Mansfield Foundation in Washington, also welcomed Prime Minister Fumio Kishida's call for a "substantial increase" in Japan's defense spending and his not ruling out the introduction of counterstrike capabilities.

Jannuzi made the remarks as senior U.S. military officers have said China could attempt to take control of Taiwan by 2027, or even as early as 2023. Speculation is also growing that North Korea may carry out a seventh nuclear test.