Mauritius will assume sovereignty over the Chagos Islands after it reached a "historic agreement" with the UK to settle a decades-long dispute, the British government announced on Thursday.

The foreign office said the UK would maintain its "strategically important" joint military base with the United States on Diego Garcia in the archipelago under the terms of the deal.

"3rd October 2024. A day to remember. A day to commemorate full sovereignty of the Republic of Mauritius over the entirety of its territory," Mauritius' Foreign Minister Maneesh Gobin later wrote on X platform.

U.S. President Joe Biden also praised the UK-Mauritius joint statement on Thursday as a "historic agreement."

"It is a clear demonstration that through diplomacy and partnership, countries can overcome long-standing historical challenges to reach peaceful and mutually beneficial outcomes," Biden said in a White House statement. 

The UK, which has controlled the region since 1814, detached the Chagos Islands in 1965 from Mauritius – a former colony that became independent three years later – to create the British Indian Ocean Territory. 

In the early 1970s, it evicted almost 2,000 residents to Mauritius and the Seychelles to make way for an airbase on the largest island, Diego Garcia, which it had leased to the United States in 1966.

In 2016, the UK Foreign Ministry extended Diego Garcia's lease until 2036, and declared the expelled islanders would not be allowed to go back.

A non-binding resolution in the United Nations General Assembly in 2019 said Britain should give up control of the islands and that it had wrongfully forced the population to leave. In the same year, the International Court of Justice also advised Britain to hand over the remote islands.

Talks on the future of the islands began between the countries in 2022 after years of the UK refusing to relinquish control. 

The deal marks a change of approach to the issue from new British Prime Minister Keir Starmer, who has said his government would be, in part, defined by a respect for international law after his Labour Party won power in July.

(With input from agencies)