The Japanese government is strengthening its monitoring of North Korea in collaboration with the U.S. as the launch window for a North Korean rocket approaches.

Japan's Asahi Shimbun said Friday that nine Aegis destroyers were deployed off the northern coast and two U.S. submarines are stationed in the East Sea.

The Japanese daily said three U.S. scout planes are closely observing the trajectory path the North Korea says the rocket will follow.

According to Asahi, this is the largest-ever joint military deployment by Japan and the U.S.