The government of Mauritius announced on Tuesday that is sending a boat to the disputed Chagos Islands in the Indian Ocean.
The archipelago is under British rule but Mauritius has won growing international support for its campaign to take back control of the islands.
The Mauritian authorities claim it is a scientific expedition with the aim of mapping the reefs around the archipelago.
The boat will also carry a group of elderly native inhabitants of the islands forced to leave their homes by the British half a century ago.
In 2019, the International Court of Justice ruled that Britain should give up control of the islands.
One of the islands, Diego Garcia, is home to an important US military base which lies at the centre of the dispute.
Britain has previously said that Mauritius can take control of the Chagos Islands once the archipelago is no longer needed for security purposes.