Indian Council of World Affairs

In May 2025, the United Kingdom (UK) signed an agreement with Mauritius on the Chagos Archipelago, for transferring of sovereignty of the Chagos to Mauritius, while retaining control over the joint UK-US military base at Diego Garcia. At that time, the US had welcomed the Treaty, as the Secretary of State Marco Rubio had said that “the agreement secures the long-term, stable, and effective operation of the joint US-UK military facility at Diego Garcia”.[i]

However, in January 2026, US President Donald Trump reversed the previous US’, stance on the issue calling the agreement, an act of "total weakness" and "great stupidity" on the part of the UK. He further mentioned that "China and Russia have noticed this act of total weakness .... and that is another in a very long line of National Security reasons why Greenland has to be acquired."[ii] However, later after speaking with British Prime Minister Keir Starmer, although he softened his criticism of the UK but remained firm regarding the US presence on Diego Garcia as he posted on Truth Social on 6 February stating that “Diego Garcia is of great importance to the national security of the US”, and that the Chagos Agreement was the “best” that the British PM “could make”. He also mentioned that “if the lease deal, sometime in the future, ever falls apart, or anyone threatens or endangers US operations and forces at the base, he retains the right to militarily secure and reinforce the American presence”.[iii] These statements highlight the importance the US attaches to its strategically located base at Diego Garcia in the Indian Ocean.

The UK-Mauritius Agreement on Chagos and the US reactions to the deal, have once again brought attention to this strategically located Diego Garcia Island in the centre of the Indian Ocean. This echoes the late 1960s, when British forces withdrew from the east of Suez, paving the way for American military entry into the Indian Ocean with the Anglo-American Agreement of 1966. Located between Asia and Africa, although geographically faraway from Washington, the base has been significant for the US to protect its interests in and around the Indian Ocean, across Asia, Africa and the Middel East.

At a time when the Indian Ocean Region (IOR) and the wider Indo-Pacific region are witnessing geopolitical shifts with enhanced interest of regional and extra regional players in the Indian Ocean, driven by the Ocean’s critical maritime routes, which plays vital role in energy supply chains, and is a geopolitical arena for asserting regional influence, projecting power and securing economic interests, any flaring up of the situation in the Chagos would further complicate the security balances in the region.

 Figure: 1
Maps Depicting Diego Garica Island and Chagos Archipelago
Source: Google Earth and Republic of Mauritius, Direcctory https://govmu.org/EN/Pages/AboutChagos.aspx 

UK-Mauritius Agreement on Chagos Islands

The Chagos Islands are located around 2,100 kilometres northeast of Mauritius, in the middle of the Indian Ocean. In 1965, the Archipelago was detached from Mauritius to create the British Indian Ocean Territories (BIOT), in exchange for a payment of £3 million, and the population on the islands was forcefully displaced to create a UK-US joint military base.[iv] Later in 1968, Mauritius was granted independence while the British retained control over the Chagos Archipelago. BIOT is currently one of the fourteen UK Overseas Territories. However, Mauritius’ Constitution includes the Chagos Archipelago as part of its territory[v] and after independence, Mauritius began to raise the issue of Chagos sovereignty transfer in international forums.[vi] The UN General Assembly (UNGA) passed many resolutions including in 2017 and 2019, calling for complete decolonisation of Mauritius.[vii] On UNGA’s request, in 2019, the International Court of Justice (ICJ), gave an advisory opinion on the matter saying that “the process of decolonization of Mauritius was not lawfully completed when that country acceded to independence” and that “the UK is under an obligation to bring to an end its administration of the Chagos Archipelago as rapidly as possible”.[viii]

Therefore, the Chagos issue has been one of the enduring sovereignty disputes in the IOR. On 22 May 2025, the governments of the UK and Mauritius concluded an agreement on the sovereignty and future of the Chagos Archipelago. The agreement provides for Mauritius to exercise complete sovereignty over the Chagos Archipelago, and allowing the UK to secure the base at Diego Garcia. As per the agreement, the UK will lease back the key military base for £101 million ($136 million) per year, for an initial period of 99 years. The period can be extended by another 40 years, if both parties agree, and can be extended again after this. The deal also entails that ‘Mauritius will not allow other powers to use the outer islands around Diego Garcia without agreement with the UK’. Mauritius will be free to arrange for resettlement of Chagossians on all the islands of the archipelago except Diego Garcia. It will also establish a marine protected area, with UK support, to protect the environment.[ix] To implement the treaty, a bill titled ‘Diego Garcia Military Base and British Indian Ocean Territory Bill’, was introduced in the British Parliament, on 15 July 2025.[x] The treaty must be ratified in both the British and Mauritian parliaments for its implementation.

Upon the conclusion of the agreement, Mauritian Prime Minister Navin Ramgoolam, stated that “it marks the culmination of nearly 60 years of struggle for dignity and justice and completes the process of decolonisation which began in 1968…” He also said that “It is not just a bilateral agreement. It is a victory for international law, for postcolonial justice, and above all, for the Chagossian people”.[xi]

Reacting to the deal the opposition in the UK, while staunchly criticized the agreement said that deal will put the UK’s security and defence at risk and also cost the UK £35 billion.[xii] The Conservatives and Reform UK argued that the deal undermines national security because of Mauritius's ties to China. Conservatives also delayed the debate in the House of Lords on the bill, as they tabled an amendment calling for a pause "in light of the changing geopolitical circumstances".[xiii] As a result, the planned deliberations in the UK parliament were delayed following a backlash from Trump and the caused by the opposition’s criticism.

India welcomed the signing of the treaty as a milestone achievement and a positive development for the region, marking the culmination of the Mauritius’s decolonization process, in the spirit of international law and a rules-based order. [xiv] India has consistently supported Mauritius’s legitimate claim over the Chagos Archipelago. With the conclusion of the agreement on Chagos, Mauritius has a much larger EEZ to secure and protect. India has been a committed development partner for Mauritius, across key sectors. India has agreed to provide assistance in the development and surveillance of the Chagos Marine Protected Area, as part of USD $680 million, special economic package for Mauritius, announced during Mauritius’ Prime Minster Navin Ramgoolam’s visit to India in September 2025.[xv] Prime Minister Ramgoolam thanked India for its support and also requested a vessel from India, for visit to Chagos to plant Mauritius flag.[xvi]

The US’ views of the treaty, while earlier supportive, has become unclear with recent statements by President Trump.

Recently, the Maldives has raised formal objection to the deal, once again reviving the Maldives-Mauritius dispute on Chagos. President Mohamed Muizzu speaking in the Maldivian Parliament, on 5 February 2026, said that Maldives has submitted formal objections regarding the deal, to the UK. The disputed maritime area between the Maldives and Mauritius covered approximately 95,000 square kilometres. In 2023, following a case filed by Mauritius, the International Tribunal for the Law of the Sea (ITLOS) had divided the overlapping 200 nautical-mile EEZs, allocating 47,232 sq kms to the Maldives and 45,331 sq kms to Mauritius. President Muizzu has rejected the maritime boundary drawn by ITLOS.[xvii] Reversing the stance of his predecessor President Ibrahim Mohamed Solih’s government, which recognised Mauritian sovereignty over the Chagos Islands, in 2022, President Muizzu said the current government is committed to reclaiming the lost maritime area. Citing historical connections with the Chagos, he said that “Maldives has a greater claim to Chagos than any other country”.[xviii] The President also announced that Maldives’ Special Economic Zone (SEZ) will be expanded to include the disputed maritime area. He said that the government will revise the Maritime Zones Act of 1996 to this effect, to formally designate a 200 nautical-mile EEZ as sovereign “Maldivian territory.” Following the President's speech, the Maldives Defence Ministry announced that the ‘Coast Guard ship and military drones have been deployed to monitor the southern waters’. President Muizzu has also offered to the US that if sovereignty is transferred to the Maldives, he would facilitate continuation of the status quo, with regard to the US presence on Diego Garcia.[xix]

Diego Garcia: Why It Is significant for the US?

Diego Garcia is the largest and most southerly island, of the Chagos Archipelago. It is attractive because of its location; the horseshoe shaped atoll, approximately 23 km long and 8 km wide, lies in the centre of the Ocean, located 3500km from both Bab-el-Mandeb and the Malacca Strait and 4200 km from Bahrain in the Persian Gulf. Given Diego Garcia’s location near hydrocarbon rich states of the Indian Ocean and its status as a major American military base, it is significant in geopolitical considerations of the IOR.

The US maintained a presence in the Indian Ocean since the British withdrawal from the region from late 1960s, which eventually resulted in the de-facto takeover of Diego Garcia by the US’. The objective of the US’ facilities at Diego Garcia “is to provide logistic support to operational forces forward deployed to the Indian Ocean and Persian Gulf areas” … ‘Its strategic location and full range of facilities make the island the last link in the long logistics chain; supporting vital US and British naval presence in the Indian Ocean and North Arabian Sea’.[xx]  

The multipurpose military base at Diego Garcia, has remained the pivot of US naval strategy in the Ocean and played a key role in the US’ military operations in Vietnam, Iraq, and Afghanistan. Recently, the US deployed B-2 bombers to counter Houthi attacks, specifically targeting their infrastructure in Yemen. Therefore, for the US, Diego Garcia is an important base facilitating the US military presence around major international shipping lanes and for projecting power across the wider IOR.

The US is also worried that the Chagos transfer will allow an opportunity for China to enhance its footprint in Mauritius, given that economic ties between Mauritius and China have grown significantly, especially since the China-Mauritius Free Trade Agreement took effect on January 1, 2021. The FTA with Mauritius is the first such agreement that China has with any African country.  China already has military presence at strategic locations in the Indian Ocean including a base at Djibouti and a presence in Gwadar, and Hambantota.

The US’ approach in the Indian Ocean is now integrated into its broader Indo-Pacific strategy which focuses on a ‘free, open and rules-based order’. Recognising the strategic significance of the Ocean, US emphasises on the need for ensuring freedom of navigation and supply chain resilience in the region. The US maintains alliances and partnerships across the IOR. In recent years, the US has also been increasing its focus on engaging with smaller states in the region, like the Maldives, Sri Lanka, Mauritius, Seychelles, and Madagascar, to counter Chinese debt-trap diplomacy. In 2023, US reopened its embassies in Maldives and in Seychelles. The US has been emphasising on minilateral and plurilateral cooperation including through platform like the Quad and the Malabar exercises. US has also been focussing on enhancing connectivity, infrastructure and countering Chinese economic influence across the Indo-Pacific, through initiatives like the Asia Enhancing Development and Growth through Energy (AEDGE) and Partnership for Global Infrastructure and Investment (PGI).[xxi] The US also plans to launch new initiatives under the I2U2 and India-Middle East-Europe Corridor (IMEC).[xxii]

Given the vital significance of region and Diego Garcia being the only military base of the US in the Indian Ocean, the Trump administration would be keenly watching how the UK’s deal with Mauritius proceeds.

Conclusion

In recent years, the IOR has witnessed increased military presence of regional and global powers, with increasing deployment of foreign ships, especially from China and also more frequently from the US and EU naval forces, as the US reaffirms it’s ‘free and open Indo-Pacific’ vision and European nations embrace the Indo-Pacific construct. The overall situation in the IOR is very dynamic. The strategic importance of the IOR surpasses regional boundaries, making it a pivotal arena in the shaping of the global balance of power. Given the geopolitical competition in the IOR, smaller regional countries like Sri Lanka, Mauritius, Madagascar, Maldives, and Seychelles, often find themselves at the centre of the turmoil due to their pivotal strategic locations. The small island nations are particularly very crucial, as they are not only sources of critical natural resources with vast maritime zones, but also play an important role in maritime defence strategy calculations.

In the case of Chagos and Diego Garcia, the US military base is also a strategic deterrence against China. The US’ stand on the issue underscores the strategic centrality of Diego Garcia for the US, in Indian Ocean geopolitics and reinforces US commitment to continued military presence, even amid shifting sovereignty arrangements. Trump’s statements are driven to an extent by concerns that a perceived weakening of the US control would create space for China, to increase its influence in the region and may weaken the US strategic leverage in the IOR. It is also driven by his ‘America first’ narrative and the preservation of US military dominance. Trump’s mention of the possibility of military use if needed to protect American base, underscores a more assertive US posture and once again highlights that the Indian Ocean is becoming an increasingly competitive and securitised space. Transatlantic ties have already been experiencing cracks, amid tariff threats and the Greenland issue, Trump’s harsh critique of the UK, a key NATO ally, which, although he later softened, but certainly reflectes conflicting priorities and differences in transatlantic relations.

Therefore, while the agreement on Chagos has been announced, its full implementation does not seem to be without obstacles, and it remains to be seen how its ratification and implementation proceeds.

*****

*Dr. Pragya Pandey, Research Fellow, Indian Council of World Affairs (ICWA)
Disclaimer: The views expressed are personal.

Endnotes

[i] UK signs Chagos deal with Mauritius to seal future of US-UK air base, 22 May 2025, https://www.reuters.com/world/uk/uk-set-sign-deal-ceding-sovereignty-chagos-islands-mauritius-2025-05-22/

[ii] In justifying Greenland bid, why Trump cited the Indian Ocean Island of Diego Garcia, 20 January 2026, https://indianexpress.com/article/explained/explained-global/greenland-trump-indian-ocean-island-diego-garcia-uk-10484849/

[iii] Twitter, https://x.com/PTI_News/status/2019485341481107683

[iv] UK ratification of the Chagos Archipelago treaty will not violate international law, 26 January 2026, https://www.chathamhouse.org/2026/01/uk-ratification-chagos-archipelago-treaty-will-not-violate-international-law

[v] The Constitution of The Republic of Mauritius, p.66, https://mauritiusassembly.govmu.org/mauritiusassembly/wp-content/uploads/2024/11/The-Constitution-Long-Upload-on-website-modify-on-28.01.22-06.04.22-.pdf

[vi] 2025 treaty on the British Indian Ocean Territory/Chagos Archipelago, 8 September 2025, House of Commons Library, https://commonslibrary.parliament.uk/research-briefings/cbp-10273/

[vii] Resolution adopted by the General Assembly on 22 June 2017, https://docs.un.org/en/a/res/71/292

[viii] Legal Consequences of the Separation of the Chagos Archipelago from Mauritius in 1965, Overview of the CASE, https://www.icj-cij.org/case/169

[ix] 2025 treaty on the British Indian Ocean Territory/Chagos Archipelago, 8 September 2025, House of Commons Library, https://commonslibrary.parliament.uk/research-briefings/cbp-10273/

https://commonslibrary.parliament.uk/research-briefings/cbp-10273/

[x] I. bid.

[xi] UK Recognises Mauritian Sovereignty Over Chagos Archipelago in Historic Agreement, 25 May 2025, https://bizweek.mu/this-is-more-than-a-bilateral-agreement-it-is-a-victory-for-international-law-for-postcolonial-justice-and-above-all-for-the-chagossian-people-said-dr-navinchandra-ramgoolam-prime-minis/news/

[xii] I.bid

[xiii] Chagos Islands debate delayed as Tories call for halt to bill

24 January 2026

https://www.bbc.com/news/articles/cp372wz0z2zo

[xiv] Statement on Chagos Treaty signed between the United Kingdom and Mauritius regarding return of Mauritian sovereignty over Chagos Archipelago, May 22, 2025, https://www.mea.gov.in/Speeches-Statements.htm?dtl/39518/Statement_on_Chagos_Treaty_signed_between_the_United_Kingdom_and_Mauritius_regarding_return_of_Mauritian_sovereignty_over_Chagos_Archipelago

[xv] India - Mauritius Joint Announcement: Special Economic Package, 11 September 2025, https://www.pib.gov.in/PressReleasePage.aspx?PRID=2165598®=3&lang=2

[xvi] India, Mauritius agree to develop and monitor Chagos Marine Protected Area, October 27, 2025, https://economictimes.indiatimes.com/news/india/india-secures-strategic-entry-in-chagos-close-to-key-us-base-diego-garcia-used-in-gulf-war-afghanistan-and-iraq/articleshow/123850629.cms?utm_source=contentofinterest&utm_medium=text&utm_campaign=cppst

[xvii] Maldives Objects to Transfer of Chagos Sovereignty to Mauritius, seeks Formal Talks with UK, 05.02.2026, https://edition.mv/news/48071?ref=cat-sub

[xviii] Geopolitical Fallout of The Maldives-Mauritius Dispute Over Chagos Islands, February 10, 2026, https://dailynews.lk/2026/02/10/p-k-balachandran/948022/geopolitical-fallout-of-the-maldives-mauritius-dispute-over-chagos-islands/

[xix] Maldives deploys military after Muizzu rejects maritime boundary with Mauritius, 05 February 2026, https://maldivesindependent.com/politics/maldives-deploys-military-after-muizzu-rejects-maritime-boundary-with-mauritius-02f7

[xx] Navy Support Facility Diego Garcia, https://cnrj.cnic.navy.mil/Installations/NSF-Diego-Garcia/About/History/

[xxi]Priority Areas, Office of the U.S. Special Coordinator for the Partnership for Global Infrastructure and Investment, https://2021-2025.state.gov/priority-areas-office-of-the-u-s-special-coordinator-for-the-partnership-for-global-infrastructure-and-investment/

[xxii] I. bid