The Maritime Self-Defense Force has begun joint drills with the aircraft carrier USS Carl Vinson and its escort vessels in the Western Pacific, the Defense Ministry said Sunday, as the U.S. strike group crept closer to the Sea of Japan.

The MSDF destroyers Samidare and Ashigara, which departed Sasebo naval base in Nagasaki Prefecture on Friday morning, are taking part in the exercises amid concerns that North Korea is preparing to conduct more missile and nuclear tests this week.

An MSDF spokesman told The Japan Times on Sunday that the drill was not based on any specific combat scenario and that "no particular country was in mind" when the drill was planned.