New York summit and diplomatic reversal

Prime Minister Andy Burnham met Donald Trump on 22 September 2026 at the United Nations General Assembly in New York, marking Burnham's international diplomatic debut. During their private discussions, Trump maintained his categorical opposition to the treaty transferring sovereignty of the Chagos archipelago to Mauritius. The American president dismissed the bilateral agreement as defective and demanded firm security guarantees for the joint military installation on Diego Garcia. Following the encounter, Burnham stated that London would review the treaty framework to address Washington's strategic objections.

“I don't support it. I think it's terrible. It was a terrible deal. [Mauritius] all of a sudden say they have ownership. Somebody has ownership that never showed up before, after decades and centuries. I think it's ridiculous.”

Terms of the suspended agreement

The sovereignty agreement, signed in May 2025 under former Prime Minister Keir Starmer, resolved decades of territorial disputes by recognising Mauritian sovereignty over the archipelago. In exchange, the treaty granted the United Kingdom and the United States continued control over the Diego Garcia base under a 99-year lease agreement. Financial stipulations committed the British government to pay Mauritius £165 million per year for the initial three years, decreasing to £120 million annually from the fourth year onwards. The strategic military installation on Diego Garcia provides operational infrastructure for Western air missions across the Persian Gulf and Indian Ocean.

London halts payments and pauses execution

British Defence Secretary Wes Streeting confirmed the operational suspension on 23 September 2026 during an interview with BBC Radio 4's Today programme. Streeting explained that the agreement cannot proceed in its current format because the United States administration has withdrawn its backing. Consequently, the British government froze scheduled financial transfers to Mauritius, withholding annual installments worth at least £120 million. British officials stated that payments will remain blocked until diplomats can negotiate revised terms that satisfy both the United States and Mauritius.

“This deal as it is currently constituted can't go ahead without American support. So we have to get a deal to a place where it commands American support as well as the agreement of the government of Mauritius and our government.”

Political background and next steps

The dispute reflects lingering diplomatic friction that originated when Keir Starmer defended the Chagos transfer in parliament against early American criticism. Relations between Washington and London had previously deteriorated over the UK's refusal to endorse American airstrikes against Iran. Burnham acknowledged that he inherited the stalled territorial dispute and maintained optimism about negotiating a modified pact alongside American partners. However, British officials privately assess that the treaty cannot advance unless Donald Trump changes his position on the sovereignty transfer.