US Secretary of State Marco Rubio told Fox News the RAF Fairford incident involved a foreign actor, going further than President Trump, who declined to rule out an Iranian link. The claim puts Washington at odds with London, where Defence Secretary Wes Streeting said it was 'too soon' to blame a foreign state for the suspected plot. Five British nationals were arrested over the plot and released on bail.

The men, all London residents aged 23 to 25, were arrested in the village of Whelford early Sunday after a local farmer reported three suspicious vans and masked men near the base. They were first held under the Explosives Act, then further arrested on suspicion of preparing a terrorist act, and were released on bail Monday as Prime Minister Andy Burnham chaired an emergency COBRA meeting on the incident. Tests found no viable explosives in the vans. One was branded Fuel2You, and Sky News found no evidence of a UK company by that name. Police are pursuing multiple lines of inquiry, including that the men acted, knowingly or unknowingly, at the behest of a foreign state.

RAF Fairford hosts the US Air Force's 501st Combat Support Wing and has served as a hub for US B-1 and B-52 bomber operations against Iran since February. Iran's embassy in London said it 'categorically rejects' speculation linking it to the plot, while a source familiar with the investigation told Reuters a motive linked to Iran was considered the most likely, with Russian sabotage and an Islamist plot also being examined.