UK Prime Minister Keir Starmer blocked Donald Trump from using RAF bases to strike Iran, amid rising tension between the US and Iran over Tehran’s refusal to sign a deal to curb its nuclear programme.The US president was thought to have withdrawn his support for Keir’s Chagos deal over the government’s refusal to give consent for the US to use UK military bases to launch bombing runs, The Telegraph reported.The US was putting together contingency plans for a direct attack on Iran, with long-range bombing and refuelling aircraft sent to the Middle East in recent days. Trump was told by defence officials that his country would be ready for war by Saturday after the largest US military build-up in the region since 2003, when America went to war in Iraq.Any US strike on Iran was likely to use the Diego Garcia military base in the Chagos Islands, the British overseas territory that the UK was planning to give away to Mauritius, and European air bases in allied countries. The US did not need consent to use Diego Garcia, but had to ask the UK govt before using RAF bases.On Wednesday, Trump told the UK to “remain strong in the face of wokeism” and not to “give away” the Chagos Islands. Posting on Truth Social, the US president said: “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, in order to eradicate a potential attack by a highly unstable and dangerous Regime.”Trump’s comments were understood to be a reference to a US request for permission to launch long-range bombing runs from RAF Fairford, a military base in Gloucestershire that hosted US air force personnel.However, the UK had yet to give consent owing to concerns raised by govt lawyers, first reported by The Times, that participating in the strikes could be a breach of international law.Govt sources said the UK was unlikely to support any pre-emptive military strike on Iran, following a similar refusal to participate in the US president’s attack on Iran’s nuclear facilities last summer.The UK could be held responsible for an illegal attack on Iran by the US under a UN edict passed in 2001, if it had “knowledge of the circumstances of the internationally wrongful act”.After Trump’s strikes on Iran last summer, ministers repeatedly refused to say whether Britain’s lawyers believed the strikes were legal.In his message on Wednesday, Trump laid out the bones of a legal justification for bombing Iran, arguing that a strike could “eradicate a potential attack by a highly unstable and dangerous Regime… [that] would potentially be made on the United Kingdom, as well as other friendly Countries”.The regime in Tehran said it would respond to any attack.The ultimate responsibility for govt legal advice on military strikes lay with Lord Hermer, the Attorney General, although it was unclear whether he had been directly consulted about the US’s use of RAF bases.Before last year’s US strikes on Iran, it was reported that Lord Hermer had produced legal advice warning that any British involvement beyond defending UK assets in the region would be unlawful. The Attorney General reportedly told ministers he had “concerns about the UK playing any role in this except for defending our allies”, including Israel.The full legal advice was never published, but Whitehall sources told The Telegraph on Thursday that the UK was still unlikely to participate in any pre-emptive strikes on Iran, indicating that the British legal position had not changed.During the last month, the Ministry of Defence deployed additional Typhoon and F-35 fighter jets to the region in anticipation of any Iranian response to an attack by the US.Trump could also launch a strike on Iran from Diego Garcia, a base it was only required to “notify” Britain about using, under the terms of a treaty between the two countries.Under Keir’s Chagos deal, the sovereignty of the islands would pass to Mauritius, while the base would be leased back at a cost of £35bn over 99 years.Trump repeatedly flipped between support for and opposition to the deal, which he said last month was an act of “great stupidity”. He then said that he believed the agreement was the best that Keir could have struck to maintain control of the base amid legal challenges from Mauritius in the international courts.On Wednesday, the US president returned to his earlier position, writing on Truth Social: “We will always be ready, willing, and able to fight for the U.K., but they have to remain strong in the face of Wokeism, and other problems put before them. DO NOT GIVE AWAY DIEGO GARCIA!”