Fresh evidence has emerged that appears to undermine the Labour Government’s central argument for transferring sovereignty of the Chagos Islands to Mauritius, namely that the controversial treaty is required to secure the long-term future of the US-UK military base on Diego Garcia.
Just days after ministers insisted in Parliament that ratifying the treaty was essential to protect the base, the United States Department of Defense has awarded a major long-term contract for operations at Diego Garcia explicitly describing the territory as the British Indian Ocean Territory.
According to a contract notice published by the US Department of Defense on 13 January, Amentum Mitie Pacific LLC has been awarded an indefinite-delivery, indefinite-quantity contract for base operating support services at Navy Support Facility Diego Garcia, British Indian Ocean Territory. The contract runs through to January 2034, with a maximum value of $656 million over its full term.
The award covers base operations, logistics and support services and was competitively procured by the US Naval Facilities Engineering Systems Command, Pacific, based in Hawaii. Initial funding for fiscal year 2026 has already been obligated.
Critics of the Chagos treaty say the contract fundamentally contradicts repeated ministerial claims that failure to ratify the UK-Mauritius agreement would leave the base legally or operationally insecure.
During the Third Reading of the Diego Garcia and British Indian Ocean Territory Bill in the House of Lords on Monday, Foreign Office minister Baroness Chapman of Darlington argued that the treaty was necessary to ensure that the UK “retains full control over this vital asset” and said it was “crucial” that the agreement be ratified “in the ever-shifting geopolitical landscape of our age”. Prime Minister Keir Starmer used the same line in PMQs yesterday in the Commons.
Opponents argue the Pentagon’s decision tells a very different story.
They point out that the United States has committed to a multi-year operational presence at Diego Garcia under UK sovereignty, without waiting for the treaty to be ratified and without any apparent assumption that sovereignty transfer is required to sustain the base.
“This contract shows that the US is planning on long-term stability at Diego Garcia as British territory,” said one campaigner involved in the legal challenge to the treaty. “If the base were genuinely on the brink of becoming inoperable without a sovereignty transfer, the Pentagon would not be signing contracts running into the next decade.”
The timing of the award is particularly striking given that ministers have repeatedly cited the risk of adverse international legal rulings as justification for urgent ratification. The Government has argued that without the treaty, legal challenges could make the base untenable within years.
Yet the US contract not only runs until 2034, but also makes no reference to any impending change in sovereignty, instead repeatedly identifying Diego Garcia as part of the British Indian Ocean Territory.
Critics say this strengthens the case that the treaty itself introduces new risks rather than resolving existing ones. Under the agreement, sovereignty would pass to Mauritius, with the UK leasing back Diego Garcia for 99 years at a cost estimated by the Government Actuary’s Department to be £34.7 billion.
Opponents warn that this would convert a sovereign military asset into a leased facility exposed to international arbitration, payment default risk and third-party treaty obligations, including Mauritius’s commitments under the Pelindaba Treaty, which prohibits nuclear weapons on African territory.
Several peers raised those concerns during the Lords debate, warning that once sovereignty is transferred, future operations at the base could become vulnerable to legal challenges or political pressure beyond UK or US control.
The US contract award also follows warnings from retired British and allied military figures that a leased base is inherently less secure than one held under sovereign control, a point previously echoed by former US officials.
While the Labour Government insists the treaty guarantees the base’s future, opponents argue the Pentagon’s own actions suggest Washington does not share that assessment.
With the Bill now returning to the House of Commons for consideration of Lords amendments, campaigners say the US contract will intensify scrutiny of the Government’s claim that the treaty is essential for security.
As one senior critic put it: “The argument that Britain must give up sovereignty to keep the base is no longer credible. The United States has just demonstrated that it is planning for the long term under British sovereignty, not Mauritian ownership.”
Claire Bullivant
