US President Donald Trump sparked fresh debate over a landmark British foreign policy decision by branding the United Kingdom’s agreement to transfer sovereignty of the Chagos Archipelago — including the strategically critical island of Diego Garcia — to Mauritius as an “act of total weakness” and “great stupidity”.

Trump’s critique, issued on social media, focused on what he framed as risks to Western security and suggested that ceding control of territory housing a major US-UK military base could embolden geopolitical rivals, particularly China and Russia, in a region of rising strategic importance.

The president’s comments also linked the dispute to his broader strategic priorities, arguing that such perceived weakness underscored his push for the United States to exercise greater influence globally.

The Chagos deal, negotiated between London and Port Louis in 2024 and still awaiting full ratification, envisages Britain relinquishing sovereignty over the Indian Ocean territory to Mauritius while retaining operational rights over the Diego Garcia base under a long-term lease.

The arrangement was crafted to reconcile international legal pressures — notably from United Nations bodies calling for decolonisation — with enduring defence cooperation.

The British government has defended the plan as essential to securing the long-term future of the joint military facility and emphasised its alignment with international law and commitments to the displaced Chagossian people.

Mauritius has rejected Trump’s intervention as irrelevant to the settled sovereignty matter, insisting that the issue is “no longer up for debate” and that ratification of the treaty will proceed.

London and Port Louis have also underlined that the agreement reflects a historic resolution of the sovereignty dispute, accompanied by provisions for environmental protection and welfare arrangements for the Chagossian community, including citizenship pathways and welfare support.

The unusual transatlantic dispute has prompted direct dialogue between the British and American leaders, with Prime Minister Keir Starmer engaging with Trump to allay concerns and reaffirm shared security interests.

Downing Street reiterated that the treaty’s implementation — including legislative steps in the House of Lords — will go ahead and stressed the continued importance of the Diego Garcia base to collective defence in the Indian Ocean and beyond.

Critics of the deal in Britain, including opposition figures, echo some of Trump’s strategic concerns but diverge on the implications for UK sovereignty and defence.

The controversy highlights the complex interplay of international law, strategic alliances and domestic politics in decisions over territory that remain pivotal to Western military operations.