US Secretary of State Rex Tilerson has been sacked and CIA director Mike Pompeo replaced him.
A spokesman for US Secretary of State Rex Tillerson said he had learned of his removal from office when he read a tweet from President Donald Trump in which he thanked him for serving as secretary of state.
Trump's tweet on Twitter thanked Tillerson, saying Pompeo would do "a great job."
Trump nominated Gina Haspell to become the first woman to head the Central Intelligence Agency (CIA).
The State Department said Tilerson had not spoken to Trump and "was not aware" of the reasons for his dismissal.