A U.S. county has instructed teachers in local schools to explain why the body of water between Korea and Japan should be called both the "East Sea" and the "Sea of Japan."

"The National Geographic Society and many other cartographic institutions, atlases and textbooks are now labeling maps of the region of East Sea with both names -- Sea of Japan and East Sea,"

Andrea M. Kane, assistant superintendent for curriculum and instruction for Anne Arundel County, said in a recent letter to the principals and teachers of public schools there. The Maryland county has around 540,000 residents.

The Sea of Japan is still more commonly used for the body of water in the U.S. and many other countries, but Koreans believe the original and correct name is the East Sea. They say the name Sea of Japan is a legacy of Japan's imperialistic past.

Koreans argue the waters should be at least dubbed both the East Sea and the Sea of Japan in official maps.

The U.S. government, however, maintains a single-name policy for the waters.

When teaching about the geography of the East Sea, if maps in texts being used in a classroom only call the body of water the Sea of Japan, it is the teacher's obligation to explain the controversy to his or her students, Kane added in the letter.

The move is the product of months of campaigning by a Virgina-based group of Koreans in the U.S. to address the issue.

The Voice of Korean Americans (VoKA) has been working to put the name East Sea into the textbooks of U.S. schools.

"Anne Arundel County is the first U.S. region that has formally distributed teaching guidelines on the East Sea," the group's head Peter Y. Kim said. (Yonhap News)