Washington: US military cyber forces launched a strike against Iranian military computer systems on Thursday as President Donald Trump backed away from plans for a more conventional military strike in response to Iran's downing of a US surveillance drone, US officials have said.

Two officials told The Associated Press on Saturday that the strikes were conducted with approval from Trump. A third official confirmed the broad outlines of the strike. All spoke on condition of anonymity because they were not authorised to speak publicly about the operation.