A transatlantic rift is brewing, and this time it centres on warplanes, warships and one of the most strategically important islands in the world.
The United Kingdom has blocked the United States from using RAF bases to launch a potential strike on Iran, a move said to have sparked anger from US President Donald Trump.
According to reports, the disagreement over British military sites lies behind Trump’s decision to withdraw support for Sir Keir Starmer’s proposed deal to hand the Chagos Islands to Mauritius.
The Bases at the Centre of the Storm
The White House is reportedly drawing up a detailed military plan for a possible attack on Iran that would involve the use of both Diego Garcia and RAF Fairford, home to America’s fleet of heavy bombers in Europe.
Defence officials are said to have briefed Trump that US forces would be ready to begin military action by Saturday, following a formidable build-up of aircraft and naval assets.
Around 50 additional fighter jets, air-to-air refuelling tankers and support aircraft have been deployed towards the Middle East. Combined with existing forces, the US would have sufficient capacity to begin sustained airstrikes by the weekend.
However, long-standing agreements mean British bases can only be used for military operations with prior approval from Number 10.
Under international law, there is no formal distinction between a country carrying out a strike and those supporting it if the latter have “knowledge of the circumstances of the internationally wrongful act”.
Reports suggest the UK has not granted permission for US forces to use British sites in the event of a strike on Tehran, amid concerns such action could breach international law.
Trump’s Chagos Broadside
On Tuesday night, Trump spoke with the Prime Minister regarding his ultimatum to Iran over its nuclear programme.
The following day, he launched a blistering attack on the Government’s proposed Chagos Islands settlement via his Truth Social platform.
“I have been telling Prime Minister Keir Starmer… that Leases are no good when it comes to Countries,” Trump wrote, criticising plans for a 100-year lease arrangement over Diego Garcia, strategically located in the Indian Ocean.
“Should Iran decide not to make a Deal, it may be necessary for the United States to use Diego Garcia, and the Airfield located in Fairford,” he added.
The UK Government has argued that the agreement with Mauritius, forecast to cost £35 billion — is necessary for security reasons and would avoid a costly legal battle over sovereignty. Under the deal announced last May, Britain would lease back Diego Garcia for 99 years at an average cost of £101 million annually.
Diego Garcia has served as a joint UK–US military base since the 1970s and remains one of Washington’s most critical strategic assets.
Legal Red Lines
There is a strong precedent in Britain’s approach to pre-emptive military action.
During the lead-up to the Iraq War, then Attorney General Lord Goldsmith advised that international law permitted force only in self-defence where an actual or imminent attack existed. He later argued a UN resolution rendered that conflict lawful.
In 2021, current Defence Secretary John Healey sought clarification in the Commons regarding US use of British bases. He was told any operation must comply with UK law and the UK’s interpretation of relevant international law.
Trump, however, suggested a strike could be justified under international law, arguing Tehran could potentially attack the UK as well as “other friendly countries”.
“DO NOT GIVE AWAY DIEGO GARCIA!” he concluded.
The Military Build-Up
Meanwhile, the US military presence in the region is reaching levels not seen since the 2003 Iraq invasion.
A second aircraft carrier strike group, led by the USS Gerald R. Ford, is expected to reach the eastern Mediterranean within days. The carrier and its escorts could defend Israel against Iranian retaliation, using fast jets and missile defence systems.
Alternatively, aircraft from the carrier could participate directly in strikes against Iran. If redeployed to the Arabian Sea, where USS Abraham Lincoln is currently positioned, the US could significantly increase sortie rates during a sustained campaign.
With combined air and naval assets, analysts say the US would have the capability to conduct continuous strikes for weeks, should Trump give the order.
Regime Change on the Table?
According to reports, Trump has been briefed on options that go beyond targeting nuclear facilities, including attempts to destabilise the regime from the air.
Such a campaign could involve efforts to assassinate Iran’s 86-year-old supreme leader, Ali Khamenei, senior commanders and leaders of the Islamic Revolutionary Guard Corps.
Analysts suggest the strategy would aim to cripple communications and command structures, potentially encouraging Iran’s regular army, the Artesh, to side with popular protests.
Preparations have also reportedly begun in Israel for the possibility of joining US strikes. Iran, meanwhile, has conducted military drills with Russia in the Gulf of Oman and the Indian Ocean, describing them as efforts to enhance “security and sustainable maritime interactions”.
Earlier this week, Iran’s Revolutionary Guards temporarily shut parts of the Strait of Hormuz and fired cruise missiles, a stark warning about the global economic consequences of escalation.
Polish Prime Minister Donald Tusk has urged Polish citizens to leave Iran immediately, warning that the opportunity to exit the country could disappear “within a few hours”.
Political Reaction at Home
Shadow Foreign Secretary Dame Priti Patel called on the Prime Minister to “scrap this appalling deal altogether”, while Liberal Democrat leader Sir Ed Davey criticised what he described as Trump’s “endless flip-flopping” over Chagos.
A Government spokesperson said:
“As routine, we do not comment on operational matters.
“There is a political process ongoing between the US and Iran, which the UK supports.
“Iran must never be able to develop a nuclear weapon, and our priority is security in the region.”
For now, Trump has not made a final decision. Two rounds of negotiations between US and Iranian representatives in Geneva have reportedly made only limited progress.
But with aircraft carriers moving into position, fighter jets massing in the region and diplomatic tensions flaring between London and Washington, the question is no longer whether the situation is serious.
It is how long the uneasy pause can hold.
