The United States will set up a rapid reaction unit of the Marine Corps in Okinawa for the defense of remote islands in southwestern Japan, Japan-U.S. diplomatic sources said Monday.

A Marine Littoral Regiment, or MLR, will be established within a few years as part of a realignment of the Marine Corps in the southern island prefecture, according to the sources, amid China's intensifying military activities in the East China Sea.

The plan is expected to be brought up at a "two-plus-two" security meeting involving foreign and defense ministers of Japan and the United States, to be held in Washington on Wednesday, the sources said.

File photo taken in February 2020 shows members of the Ground Self-Defense Force taking part in a drill with the U.S. military at the Blue Beach training area in Kin, Okinawa Prefecture. (Kyodo)

During the talks, the two sides also plan to agree on including outer space within the remit of Article 5 of their bilateral security agreement, as Japan seeks to prevent attacks on its satellites amid an increasing need to use them for monitoring and gathering information on the military movements of other countries, they said.

Article 5 states Washington will defend territories under Tokyo's administration from armed attack.

Chinese Foreign Ministry spokesman Wang Wenbin said at a press conference in Beijing on Tuesday that Japan and the United States should ensure their alliance "does not harm the interests of a third party or regional peace and stability."

The spokesman expressed hope that Tokyo and Washington will heed the concerns of countries in the region and do more to enhance mutual trust among nations in the area.

The plans to set up a new unit in Okinawa could trigger a backlash from locals, however, as the island prefecture already bears the heavy burden of hosting about 70 percent of the total amount of land used exclusively for U.S. military installations in Japan.

The move comes as Tokyo and Washington have been making efforts to beef up deterrence and response capabilities in southwestern Japan near Taiwan, a self-ruled democratic island that Beijing regards as a breakaway province to be reunified with the mainland, by force if necessary.

File photo taken in February 2022 shows U.S. Marine Corps personnel during training in the Northern Training Area in Okinawa Prefecture. (Kyodo) 

China has been increasing its military assertiveness in the South and East China seas, with its coast guard vessels repeatedly entering Japan's territorial waters around the Senkaku Islands, a group of Tokyo-controlled uninhabited islets, which China claims and calls Diaoyu.

U.S. President Joe Biden has said the Senkakus fall under Article 5.

Consisting of about 1,800 to 2,000 personnel per unit, MLRs are capable of flexibly deploying small groups of marines to remote islands for securing footholds to attack enemies and support U.S. or allied warships.

The new unit in Okinawa is hoped to counter potential advances by the Chinese military.

In March, the U.S. Indo-Pacific Command said it established an MLR in Hawaii, the first of its kind in the Marine Corps. Biden's administration is also considering creating another MLR in Guam by reforming two existing regiments in the prefecture, according to the sources.

The MLR deployment in Okinawa is unlikely to affect a current U.S. Marine Corps transfer plan of relocating around 9,000 personnel to Guam and Hawaii among other locations while leaving some 10,000 in Okinawa, the sources said.

In its three key defense documents updated last month, the Japanese government pledged to strengthen Self-Defense Forces units in Okinawa to defend the southwestern remote islands, while calling China "the greatest strategic challenge."