Tensions between Tokyo and Seoul flared again Monday when South Korea began maritime research in waters around islets under its control that are also claimed by Japan.
The move, which involves the islets called Takeshima in Japan and Dokdo in South Korea, proceeded despite repeated warnings from Tokyo.
Foreign Ministry sources said Tokyo will consider dispatching survey ships to the area should Seoul ignore the request and conduct the survey within what Japan says is its exclusive economic zone, based on its claims to the disputed islets.