US President Donald Trump has warned that the United States could take military action to secure and reinforce its presence at Diego Garcia if any future arrangement threatens access to the strategically vital joint US-UK military base, following the United Kingdom’s treaty with Mauritius over sovereignty of the Chagos Archipelago.
In a post on Truth Social on Thursday (local time), Trump said he had held “very productive discussions” with British prime minister Keir Starmer on the future of Diego Garcia, which hosts one of the most important US military installations in the Indian Ocean.
“If the lease deal, sometime in the future, ever falls apart, or anyone threatens or endangers US operations and forces at our Base, I retain the right to Militarily secure and reinforce the American presence in Diego Garcia,” Trump wrote.
Strategic importance to US national security
Emphasising the base’s significance, Trump said Diego Garcia’s central location in the Indian Ocean made it critical to US national security and global military operations.
“It is the site of a major US Military Base, strategically situated in the middle of the Indian Ocean and, therefore, of great importance to the National Security of the United States,” he said, crediting recent US military successes to the strength of American warfighters, modern equipment and the global positioning of US bases, including Diego Garcia.
Trump also rejected what he described as attempts to undermine the US presence at the base, saying, “Let it be known that I will never allow our presence on a Base as important as this to ever be undermined or threatened by fake claims or environmental nonsense.”
UK-Mauritius treaty and lease arrangement
Trump’s remarks refer to the UK-Mauritius Treaty signed in 2025, under which Mauritius exercises full sovereignty over the Chagos Archipelago, while the UK retains rights to operate Diego Garcia for an initial 99-year lease.
The agreement includes long-term financial payments by the UK, with an option to extend the lease by a further 50 years, according to public estimates cited by Reuters.
While acknowledging that Prime Minister Starmer had negotiated “the best deal he could make” under the circumstances, Trump’s comments underline continued concerns in Washington over the long-term implications of the arrangement.
Shift in tone, but concerns remain
The warning marks a slight shift from Trump’s earlier criticism of the deal. In January, he described the UK’s decision to transfer sovereignty as an act of “great stupidity” and “total weakness”, arguing it could invite strategic attention from rivals such as China and Russia.
Downing Street has confirmed that Trump and Starmer discussed Diego Garcia during a recent call. “The leaders recognized its strategic importance,” a No 10 spokeswoman said, adding that both governments agreed to continue working closely to guarantee the future operation of the base, Reuters reported.
Why Diego Garcia matters
Washington has described Diego Garcia as an “all but indispensable platform” for military operations across the Middle East, South Asia and East Africa. The base supports long-range bomber missions, logistics, intelligence collection and military communications, and hosts around 2,500 US military and civilian personnel.
It has been used in US operations ranging from Afghanistan and Iraq to more recent deployments, including the stationing of nuclear-capable B-2 Spirit bombers amid air operations targeting Yemen’s Houthi rebels. The US has also acknowledged that the base was previously used for secret flights transporting terror suspects.
How will US control of Chagos affect India?
India has quietly encouraged the return of sovereignty over the Chagos Archipelago to Mauritius, aligning with its broader strategic interests in the Indian Ocean and its concerns over China’s growing footprint in the region.
New Delhi’s position is shaped not only by contemporary security considerations but also by historical experience. The US decision to establish a full-scale military base on Diego Garcia was taken during the Richard Nixon administration, which had backed Pakistan during the 1971 India-Pakistan war, revealed in several papers declassified later cited by the national security archives of George Washington University. At the time, Washington dispatched the 7th fleet of its navy, including the USS Enterprise, into the Bay of Bengal in a move widely seen as an attempt to pressure India.
India, backed by the then Soviet Union, proceeded with military operations that led to the creation of Bangladesh, ahead of the arrival of the US carrier group.
More recently, India has deepened its engagement with Mauritius. In September last year, New Delhi announced a $680 million economic assistance package, comprising grants and lines of credit, to support development projects in the island nation. The assistance also includes support for monitoring the marine protected area around the Chagos Archipelago, according to ANI.
The current 99-year lease arrangement between the UK and Mauritius ensures continued US access to the Diego Garcia base while preserving Mauritian sovereignty. However, any move by the US to assume direct control over the Chagos Archipelago would strip Mauritius of ownership, rendering existing agreements – including India’s $680 million assistance package – automatically void. Such a development could complicate India’s strategic and economic interests in the Indian Ocean region.
Trump’s stance contrasts with that of the Biden administration, which had welcomed the UK-Mauritius agreement as a diplomatic solution to a long-standing sovereignty dispute while preserving military access.
The deal has drawn criticism within the UK as well, with the Conservative Party arguing it weakens Britain’s strategic position and risks straining security ties with Washington. Mauritius, meanwhile, has said its sovereignty over the islands is “unequivocally recognized” under international law and has called for swift implementation of the treaty.