Given enough time, North Korea will likely succeed in developing a nuclear warhead small enough to be mounted on a ballistic missile capable of directly striking Japan, the Self-Defense Forces' highest-ranking officer warned Tuesday.

Facing reporters at the Foreign Correspondents' Club of Japan in Tokyo, Adm. Katsutoshi Kawano declined to comment on whether Tokyo believes the North has already acquired such a capability, but said that given more time, Pyongyang would likely master this technology, putting Japan in grave danger.

"So it is very important for the international community to keep putting pressure on the North to renounce its nuclear weapons and ballistic missiles programs," Kawano said.