Donald Trump has publicly complained that British prime minister Keir Starmer once blocked US forces from using the Diego Garcia base to strike Iran, saying he was 'very disappointed' by the intervention. British officials had warned Washington that authorising strikes from UK-controlled territory could breach international law, setting up a rare public dispute between the allies.
Diego Garcia sits in the central Indian Ocean roughly 750km northeast of Mauritius and has been the linchpin of long‑range US military reach since a 1966 US lease of the island from Britain. In May 2025 Britain signed an agreement to transfer sovereignty over the Chagos archipelago to Mauritius, while arranging for the Diego Garcia base to be leased back to the UK and the US — a compromise intended to reconcile sovereignty claims with strategic basing needs.
In the early days of the latest Iran crisis London initially refused US requests to use Diego Garcia and the RAF base at Fairford, citing international law. Starmer then softened his stance on March 1, authorising limited, specific defensive uses of Diego Garcia for US forces, a narrow concession that underlined the legal and political tightrope the government is walking.
Trump has since framed Starmer's initial refusal as unprecedented and complained that the prime minister 'took too long' to change his mind because he was worried about legality. British reporting in February suggested that the refusal prompted Trump to threaten withdrawing support for the Chagos handover to Mauritius, illustrating how military cooperation and diplomatic deals can be leveraged against one another.
The refusal and its aftermath must be read against a rapid escalation between the United States, Israel and Iran. On February 28 US and Israeli strikes on Iranian targets reportedly killed Supreme Leader Ali Khamenei, provoking a series of Iranian retaliatory attacks by the Islamic Revolutionary Guard Corps that struck multiple US positions in the region and targeted the aircraft carrier USS Lincoln with ballistic missiles. The confrontation has already produced casualties, damage across the Middle East and heightened fears of a widening conflict.
The incident exposes several strategic tensions. First, rule‑of‑law considerations in allied capitals can constrain US military options even when operational demand is high; that is significant when long‑range basing such as Diego Garcia is scarce and politically fraught. Second, the episode highlights the political sensitivity of basing arrangements: Britain must balance its legal obligations and domestic politics with the operational expectations of its closest ally.
The future of Diego Garcia as an operational hub will be shaped as much by legal and diplomatic architecture as by runway length or ordnance stocks. Mauritius, as the incoming sovereign, now occupies a stronger bargaining position and could impose conditions that complicate future US and UK use. Washington may seek alternative access in the region, increase forward naval deployments, or push harder for bilateral guarantees that insulate military operations from legal disputes.
What to watch next is how the UK and US operationalise the March concession without further public spats, whether Washington moves to diversify basing options in the Indian Ocean, and how the Chagos handover influences allied burden‑sharing in a tense regional climate. The episode is a reminder that legal and political constraints inside allied democracies can materially shape the conduct of high‑stakes military operations.