Diego Garcia and the Chagos Deal: Why the Handover Is Stuck on a 1966 Treaty

Diego Garcia is a joint U.S.-UK military base on an island that Britain agreed to hand to Mauritius, and the agreement is stuck because the one country whose consent it needs, the United States, will not give it. As of the latest reporting we could verify, from April 2026, the treaty cannot take effect.

Orientation. The Chagos Archipelago lies in the Indian Ocean. Britain detached it from Mauritius in 1965, before Mauritius became independent in 1968. A 2025 UK-Mauritius treaty would transfer sovereignty while keeping Diego Garcia available to the U.S. and UK. This explainer sets out how the pieces fit, and flags that we found no verified reporting after April.

Why Diego Garcia Matters Now

Diego Garcia hosts a joint U.S.-UK military base. The question of who owns the island has become urgent because of the war with Iran. In February 2026, President Trump posted "DO NOT GIVE AWAY DIEGO GARCIA!", suggesting the base might be needed for operations against Iran. In January he had called the deal an "act of great stupidity." The National reported on February 18 that he wrote: "Should Iran decide not to make a deal, it may be necessary for the United States to use Diego Garcia." The same report notes that the State Department said on February 17 that it supported the UK's agreement with Mauritius, which contradicted his stance. Those statements are recounted in an analysis by Tom Frost, published by Maritime Executive and first appearing in The Conversation on April 16, 2026.

What the Chagos Dilemma Actually Means

The dilemma is that two things are true at once. International court decisions have found the removal of Chagossians and the detachment of the islands illegal, according to Frost. And the base is militarily valuable to two allies. The treaty tries to reconcile them by transferring sovereignty while leasing the base back.

Under the 2025 treaty, Mauritius would let the U.S. and UK access, maintain and invest in the Diego Garcia base for an initial 99 years, extendable by mutual agreement. The UK would pay Mauritius an average of £101 million a year (in 2025-26 prices). Reported totals differ by source: Frost cites about £3.4 billion, while The National cites £35 billion over the century. We do not reconcile the figures here, and readers should treat any single total with caution.

The Geography of the Base

Diego Garcia sits in the middle of the Indian Ocean, far from any continent. That isolation is part of its value: it gives forces a location reachable by sea and air without depending on a neighbouring country's permission. For a comparison with how geography creates strategic leverage elsewhere, see our explainers on the Strait of Malacca and Bab el-Mandeb.

How a Sovereignty Dispute Would Work in Practice

The treaty has a legal trap. It cannot take effect unless a 1966 UK-US treaty is amended, which requires an exchange of letters between the two governments. Frost reports that the U.S. has refused to provide its letter. Without it, the UK has no way to complete the handover, and he reports that the government shelved the legislation after the U.S. withdrew its support. He describes the deal as effectively dead, since the bill ran out of parliamentary time and there are no plans to reintroduce it. That is his assessment, not an official statement.

How the UK and Mauritius Tried to Resolve It

The parties used a lease-back model: sovereignty to Mauritius, operations to the U.S. and UK. Domestic politics complicated it. Conservative leader Kemi Badenoch called the payments unacceptable and questioned Mauritius's ties to China. Reform UK leader Nigel Farage claimed the deal has no legal basis. Those are claims by opposition politicians, and we have not verified them.

"We will spare no effort to seize any diplomatic or legal avenue to complete the decolonisation process."

- Dhananjay Ramful, Mauritius foreign minister, Maritime Executive

The Alternatives to a Deal, and Why They Are Not Enough

• Keep the status quo. The UK keeps sovereignty, but court rulings and Mauritius's campaign keep the legal question open.
• Legal action. Mauritius's foreign minister, Dhananjay Ramful, said: "We will spare no effort to seize any diplomatic or legal avenue to complete the decolonisation process." Frost expects pursuit at the United Nations, possibly the International Court of Justice.
• Renegotiate with the U.S. at the table. The 1966 agreement means any lasting solution needs Washington.

None settles the matter alone. A status quo leaves a legal cloud. Litigation takes years and cannot compel the U.S. to sign.

What the Base Changes Operationally

This article does not describe what forces are stationed or how they operate there. The public point is narrower: the base is available to the U.S. and UK now, and the treaty, if it ever took effect, would preserve that access for decades under Mauritian sovereignty. Trump's February post suggests Washington sees value in keeping the arrangement unchanged.

Common Misconceptions About Diego Garcia

• "The handover already happened." It has not. The treaty requires a U.S. letter that has not been given.
• "The base would close." The treaty is designed to keep it open for an initial 99 years.
• "The question is only about Iran." The legal dispute began in 1965 and has involved international courts. The Iran war added urgency.

Limits and Risks in Using Diego Garcia as Leverage

A base can become leverage for its users and for those who contest its status. Mauritius's legal campaign raises the political cost of staying put. The Chagossians have their own claims: on March 31, 2026, they won a challenge in the British Indian Ocean Territory Supreme Court that overturned a 2004 law denying them a right of abode. Under the treaty they would have gained a right to return to islands other than Diego Garcia. Their interests do not align neatly with either government.

Future Implications

Three paths are plausible: a revived treaty with U.S. consent, a long legal fight at the UN, or an unresolved status quo. We found reporting that Mauritius would give London until the end of July 2026 before deciding its position, but we found no reporting on what followed. Readers should check current news before relying on this analysis.

Closing assessment. The Diego Garcia dispute is not about whether the base exists. It is about who holds legal title, and whether three governments can agree on terms that all can defend at home. The decisive factor is Washington, and as of April it had said no.

FAQs about Diego Garcia and the Chagos deal

What is the Chagos Islands treaty?

A 2025 UK-Mauritius treaty that would transfer sovereignty of the Chagos Archipelago to Mauritius while keeping the Diego Garcia base available to the U.S. and UK for an initial 99 years.

Why is the treaty stalled?

It requires an amendment to the 1966 UK-US treaty through exchanged letters. According to Tom Frost, the U.S. has refused to provide its letter.

How much would the UK pay Mauritius?

An average of £101 million a year in 2025-26 prices. Reported totals differ by source, from about £3.4 billion to £35 billion over the century, so treat any single figure with caution.

What has Mauritius said it will do?

Foreign Minister Dhananjay Ramful said Mauritius would spare no effort to seize any diplomatic or legal avenue to complete the decolonisation process.

Is the information current?

The latest reporting we could verify is from April 2026. We found nothing verified after that date, so check current news.