TOKYO—Japan plans to spend around $10 billion to become the largest customer outside the U.S. for Lockheed Martin Corp.’s F-35 jet fighters, as it responds to a rising China and pressure from President Trump to spend more on American military hardware.

The cabinet of Prime Minister Shinzo Abe on Tuesday approved an increase of Japan’s existing order for 42 F-35s to 147 of the aircraft as part of new defense plans that include the development of Tokyo’s first post-World War II aircraft carriers.