The U.S. military plans to strengthen the functions of its command headquarters in Japan, as it aims for smoother cooperation with the Asian nation's Self-Defense Forces in tackling security threats posed by China and North Korea, diplomatic sources said Sunday.

Japan and the United States are expected to agree on the review of their command and control operations when Prime Minister Fumio Kishida and President Joe Biden hold talks in Washington in April, the sources said, adding it would be included in a joint statement.

Tokyo and Washington are likely to discuss the details of such issues ahead of two-plus-two talks involving their defense and foreign ministers, which will be held by the end of this year, the sources said.

File photo taken in June 2022 shows the inside of the air traffic control tower at the U.S. Yokota Air Base in western Tokyo. (Kyodo)

The move comes as Japan and the United States have bolstered their defense ties with the security environment in Asia becoming unstable amid China's assertiveness toward Taiwan and North Korea's continuous missile and nuclear weapons development.

Japan and the United States will also work on further steps to enhance their response capabilities. Tokyo decided in 2022 to acquire the capability to strike enemy bases even under Japan's war-renouncing Constitution.

Japan is set to establish a joint headquarters to command its ground, maritime and air forces by the end of March 2025. Kishida's government is aiming to deepen cooperation between the U.S. military and the joint headquarters.

Currently, the U.S. Indo-Pacific Command, responsible for Japan, has its headquarters in Hawaii and the different time zone and physical distance hampers the efficient interaction of Japanese forces and the U.S. military.

There is concern that if the U.S. military in Japan reinforces its functions along with the SDF, it would be difficult to separate its jurisdiction and authority from that of the Indo-Pacific Command, some analysts said.

Last week, U.S. Deputy Secretary of State Kurt Campbell told reporters in Tokyo that Washington welcomes Japan's efforts to boost its defense capabilities, adding a related announcement may be made after the upcoming summit.

Kishida is set to meet with Biden in Washington on April 10. The prime minister is scheduled to visit the United States as a state guest, the first such visit by a Japanese leader since Shinzo Abe in 2015.

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