The UK government insisted on Monday that the sovereignty of the Falkland Islands and Gibraltar was "not up for negotiation" after it said it would return a remote archipelago to Mauritius.
Britain announced on Thursday that it would hand back the Chagos Islands in the Indian Ocean to former colony Mauritius but that it would maintain a key military base there.
Argentine Foreign Minister Diana Mondino reacted by saying that Argentina would "recover full sovereignty" over the Falklands — the disputed British overseas territory in the South Atlantic Ocean.
"We celebrate this step in the right direction," Mondino said in a post on Instagram, hailing the move as a "milestone".
"Travelling the path we have begun, with concrete actions and not empty rhetoric, we are going to recover full sovereignty over our Malvinas Islands," he said, using the Argentinian name for the archipelago
When asked about Mondino's comments, Prime Minister Keir Starmer's official spokesman told reporters that the return of the Chagos would have "no bearing on other overseas territories".
He said the deal with Mauritius should not be seen as a precedent for other disputes because Chagos was "a unique situation based on its unique history and circumstances".
"British sovereignty of the Falkland Islands or Gibraltar is not up for negotiation," the spokesman added.
Gibraltar is a British enclave off southern Spain that is claimed by Madrid.
The UK government has been under pressure for decades to hand over the Chagos Islands to Mauritius, including from the International Court of Justice.
But it had resisted because of the military base on Diego Garcia island, which plays a key role for US operations in the Indian Ocean and Gulf.
At the start of talks last year, the British and Mauritian governments agreed that the base would continue to operate whatever the outcome.
The Falklands, home to just over 3,000 people, lie nearly 13,000km from London and some 480km from the coast of Argentina.
Britain sent a military taskforce to reclaim the islands in 1982 after Argentinian troops invaded and claimed sovereignty.
