US president Donald Trump has shaken up his core team yet again, replacing H.R. McMaster as national security adviser with John Bolton.

Bolton is the president's third national security adviser in 14 months. The 69-year-old has long been a polarizing figure in Washington foreign policy circles, advocating hardline positions on stopping Pyongyang from getting nuclear weapons. He also supports getting rid of the 2015 Iran nuclear deal, a pact Trump also heavily criticized. Trump had clashed with McMaster, a respected three-star general, and talk that McMaster would soon leave the administration had picked up in recent weeks. The White House said McMaster's exit had been under discussion for some time and stressed it was not due to any one incident.