The U.S. Marines has set up a littoral regiment in Okinawa capable of a flexible and rapid response, to bolster the defense of remote islands in southwestern Japan amid China's increased military assertiveness at sea.

The existing 12th Marine Regiment based in Okinawa Prefecture was reorganized into the 12th Marine Littoral Regiment from Wednesday.

"We're proud to be here in the First Island Chain, and a force prepared to respond to contingencies wherever and whenever required," said Col. Peter Eltringham, commanding officer of the new regiment, at a ceremony at Camp Hansen in Okinawa.

The First Island Chain refers to an area stretching from Japan's southwestern Nansei island chain — which includes the Japan-controlled Senkaku islets, also claimed by China — to Taiwan and the Philippines.

The littoral regiment, consisting of about 2,000 personnel, is the Marines' second. The first was set up in Hawaii in March 2022, while another is also being planned for another location by 2027.

The Japanese and U.S. governments confirmed the regiment's establishment at the so-called two-plus-two talks involving defense and foreign ministers in January.

The ceremony was attended by around 200 people, including Gen. Yasunori Morishita, chief of staff of Japan's Ground Self-Defense Force.