Donald Trump has sacked his national security adviser John Bolton, telling him "his services are no longer needed".
The US president tweeted: "I informed John Bolton last night that his services are no longer needed at the White House.
"I disagreed strongly with many of his suggestions, as did others in the Administration".
Mr Trump added that he would name a replacement next week.
He later added: "I asked John for his resignation, which was given to me this morning.
"I thank John very much for his service. I will be naming a new National Security Advisor next week."
In a tweet, Mr Bolton appeared to dispute Mr Trump's account of his resignation, saying he had offered to stand down last night.
"I offered to resign last night and President Trump said, "Let's talk about it tomorrow," Mr Bolton said.
His firing came as a surprise to many in the White House. Just an hour before Trump's tweet, the press office announced that Mr Bolton would join Secretary of State Mike Pompeo and Treasury Secretary Steven Mnuchin in a briefing.
Mr Bolton was always an unlikely pick to be Mr Trump's third national security adviser, with a world view seemingly ill-fit to the president's isolationist "America First" pronouncements.
He's espoused hawkish foreign policy views dating back to the Reagan administration and became a household name over his vociferous support for the Iraq War as the US ambassador to the UN under George W. Bush.
He even briefly considered running for president in 2016, in part to make the case against the isolationism that Mr Trump would come to embody.
Inside the administration he advocated caution on the president's whirlwind rapprochement with North Korea and against Mr Trump's decision last year to pull US troops out of Syria.
He masterminded a quiet campaign inside the administration and with allies abroad to convince Mr Trump to keep US forces in Syria to counter the remnants of the Islamic State and Iranian influence in the region.
Mr Bolton was named Mr Trump's third national security adviser in April 2018 after the departure of Army General H.R. McMaster.
