THE HAGUE, Netherlands (AP) — Judges at the United Nations' highest court are listening to arguments in a case focused on the legality of British sovereignty over the Chagos Islands in the Indian Ocean, including Diego Garcia, where the U.S. has a major military base.

Mauritius argues that the Chagos archipelago has been part of its territory since at least the 18th century and was unlawfully taken by the U.K. in 1965, three years before the island nation gained independence from Britain.

Britain insists it has sovereignty over the archipelago, which it calls the British Indian Ocean Territory.

The U.K. sealed a deal with the U.S. in 1966 to use the territory for defense purposes. Washington maintains a forward operating location there for aircraft and ships that contribute to regional and global security.