The United Kingdom's troubled agreement to hand sovereignty of the Chagos Islands to Mauritius edged closer to collapse on Tuesday after the Trump administration signalled it was prepared to take formal steps to prevent the transfer, according to senior officials briefed on the matter. President Trump, who has described the deal as a dangerous concession that could jeopardise the strategic Diego Garcia military base, is understood to have directed the State Department to communicate Washington's opposition directly to both London and Port Louis.

The White House's intervention represents a significant escalation from its earlier rhetorical opposition to the agreement, which Prime Minister Keir Starmer's government negotiated in late 2024 and has sought to ratify despite sustained criticism from both the Conservative opposition and elements of the Labour Party. American officials have raised concerns that a Mauritius-controlled Chagos archipelago could allow Chinese influence to encroach on Diego Garcia, one of the most strategically important Western military installations in the Indo-Pacific.

For Starmer, the development lands as a profound diplomatic embarrassment. His government had presented the Chagos deal as a principled resolution of a decades-old colonial dispute, only to find the agreement opposed by Washington at almost every turn. Conservative Party leader Kemi Badenoch moved quickly to renew her calls for the government to formally abandon the agreement, arguing that no deal acceptable to Mauritius could simultaneously satisfy American security requirements.

Mauritian Prime Minister Navin Ramgoolam has publicly insisted his government will not renegotiate terms that took years to finalise, setting up a three-way impasse between London, Washington and Port Louis. British Foreign Secretary David Lammy is expected to hold emergency consultations with his American counterpart in the coming days in an attempt to find language that could preserve some form of agreement, though officials privately acknowledge the window for compromise is narrowing sharply.

Analysts noted that Trump's willingness to openly humiliate a close ally over the issue reflects a broader pattern of the administration treating the UK as a pliable partner rather than an equal one. 'This is less about Chagos and more about demonstrating that Washington sets the terms on basing rights globally,' said one former senior British defence official. With Parliament due to debate the matter later this week, Starmer faces mounting pressure from within his own caucus to either secure unambiguous American backing or withdraw the deal entirely.