US President Donald Trump on Thursday picked as his new national security adviser John Bolton, a hawk who has advocated using military force against Iran and North Korea and has taken a hard line against Russia.
Mr Trump announced in a tweet he was ousting HR McMaster, his current national security adviser. Mr Bolton, 69, is a former US ambassador to the United Nations and is a staunch opponent of Iran nuclear deal. He becomes the president's third national security adviser in 14 months.
Mr Trump has repeatedly clashed with Mr McMaster, a respected three-star general, and talk that Mr McMaster would soon leave the administration had picked up in recent weeks.
His departure follows Mr Trump's dramatic ouster of Secretary of State Rex Tillerson last week.
It also comes after someone at the White House leaked that Mr Trump was urged in briefing documents not to congratulate Russian President Vladimir Putin about his recent re-election win. He did it anyway.
Mr McMaster was brought in after Mr Trump's first national security adviser, Michael Flynn, was dismissed.
The US President tweeted that Mr McMaster has done "an outstanding job & will always remain my friend". He added that Mr Bolton will take over April 9.
Mr Bolton, probably the most divisive foreign policy expert ever to serve as UN ambassador, has served as a hawkish voice in Republican foreign policy circles for decades.
He met with Mr Trump and White House chief of staff John Kelly in early March to discuss North Korea and Iran. He was spotted entering the West Wing earlier Thursday.