South Korea plans to dispatch military officers to the ongoing bilateral U.S.-Japan field training exercise to boost cooperation with the allies, Seoul officials said Wednesday.

The Keen Sword exercise is the latest in a series of bilateral field training exercises since 1986 involving the U.S. military and Japan Self-Defense Force designed to increase combat readiness and interoperability between the two sides.

"Two or three lieutenant colonel-level South Korean officers from the defense ministry and the Joint Chiefs of Staff are to participate in the exercise as observers," a ministry official said, requesting anonymity.

"Their participation aims to contribute to boosting the three-way security cooperation," he said, noting that Seoul has sent a handful of troops to the Washington-Tokyo biennial exercise since 2010 at the request of the U.S. troops. 

This year's Keen Sword brought about 10,000 U.S. personnel and 30,000 troops from Japan who have carried out diverse programs at military installations throughout mainland Japan, Okinawa and in the waters surrounding the Asian country, according to U.S. Forces Japan.   

Though the three nations have vowed to enhance trilateral cooperation, Seoul's participation in the exercise is expected to be a source of controversy at home and abroad.  

Relations between the two Asian countries have been soured over historical and territorial rows, and the military cooperation with Japan has been widely opposed by the people here, many of whom still resent Japan for its brutal 1910-45 colonial rule of the Korean Peninsula.

The drill also came at a time when Japan has been engaged in a bitter dispute with China over an East China Sea island, called the Senkaku in Japan and Diaoyu in China. Japan has said the exercise will be held east of its major southern island of Kyushu but not in the East China Sea. (Yonhap)