Diego Garcia, a British Indian Ocean Territory and the largest of the islands in the Chagos Archipelago

Sign up to our Next Africa newsletter and follow Bloomberg Africa on Twitter

The African Union urged the U.K. to comply with a United Nations resolution calling for it to withdraw from the Chagos Archipelago in the Indian Ocean, which is considered part of Mauritius.

The U.K. is under increased international pressure to give up its last territory in Africa since the International Court of Justice ruled that the 1965 excision of the islands from Mauritius had been unlawful. The UN General Assembly affirmed the ruling in May and set a six-month deadline that expired Friday.

Almost all African nations support the resolution. AU Chair Moussa Faki Mahamat “requests the international community to continue its support to the Republic of Mauritius for a complete decolonisation of the Chagos Archipelago,” according to a statement on the website of the organization.

Read more about the Chagos Archipelago dispute here

The U.K. argues it can’t give up the Chagos Archipelago for security reasons. It’s leased the biggest island to the U.S., which runs a military base there that supports operations in the Middle East and Afghanistan.