White House national security adviser John Bolton has resigned at the request of President Donald Trump, who said he called for the resignation due to numerous policy disagreements.

Key points: Mr Bolton was a chief architect of Mr Trump's strong stance on Iran

Mr Bolton was a chief architect of Mr Trump's strong stance on Iran Just an hour before Mr Trump's tweet, Mr Bolton was announced to appear in a briefing

Just an hour before Mr Trump's tweet, Mr Bolton was announced to appear in a briefing Mr Bolton had sometimes been at odds with US Secretary of State Mike Pompeo

Mr Trump announced the decision on Twitter: "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, and therefore 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."

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But Mr Bolton offered a different version of events on Twitter, saying he offered to resign on Monday (local time) "and President Trump said, 'Let's talk about it tomorrow'."

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Mr Bolton, a leading foreign policy hawk who was Mr Trump's third national security adviser, was widely known to have pressed the President for a harder line on issues such as North Korea.

He was also a chief architect of Mr Trump's strong stance on Iran, and had advocated a tougher approach on Russia and Afghanistan.

Mr Bolton's ouster may have came as a surprise to many in the White House. Just an hour before Mr 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.

A White House official said Mr Bolton had departed the premises after Mr Trump's tweet and would no longer appear as scheduled.

'I'm never surprised'

Mr Bolton, right, took up the post in April 2018, replacing H.R. McMaster. ( AP: Susan Walsh )

When asked about whether Mr Bolton's departure would make it easier for the administration to accomplish Mr Trump's foreign policy agenda, US Secretary of State Mike Pompeo said there were many times they disagreed.

"There were definitely places that the ambassador and I … had different views about how we should proceed," Mr Pompeo said.

"I'm never surprised," he added when a reporter asked whether Mr Bolton's sacking was news to him.

Mr Bolton, who took up the post in April 2018, replacing H.R. McMaster, had sometimes been at odds with Secretary of State Mike Pompeo, one of Mr Trump's main loyalists.

Mr Bolton and Mr Pompeo have had policy disagreements in the past. ( AP: Andrew Caballero-Reynolds )

Mr Bolton was also opposed to Mr Trump's now-scrapped notion to bring Taliban negotiators to Camp David last weekend to try to finalise a peace deal in Afghanistan.

Mr Trump had sometimes joked about Mr Bolton's image as a warmonger, reportedly saying in one Oval Office meeting that "John has never seen a war he doesn't like."

Mr Trump's North Korea envoy, Stephen Biegun, is among the names floated as possible successors.

"Biegun much more like Pompeo understands that the President is the President, that he makes the decisions," said a source close to the White House.

Also considered in the running is Deputy Secretary of State John Sullivan, who had been expected to be named US ambassador to Russia.

White House spokeswoman Stephanie Grisham said "many, many issues" led to Mr Trump's decision to ask for Mr Bolton's resignation, but would not elaborate.

Reuters/AP