Amid China's military expansion and assertiveness in regional waters, Japan plans to develop a large underwater drone that will automatically navigate the ocean to collect information, a government source said Sunday.

The Defense Ministry has decided to mention the plan, which is aimed at boosting capabilities to guard remote islands, in its policy document outlining Japan's defense capabilities through the five years from April 2019.

Prime Minister Shinzo Abe's Cabinet aims to approve the defense policy document in mid-December, according to the source.