Donald Trump is replacing national security adviser HR McMaster with the hawkish former Ambassador to the United Nations John Bolton in the latest administration shake-up.

In a sign of the administration’s unusually high rate of turnover, the pro-Iraq war hardliner will become Mr Trump’s third National Security Adviser.

"General McMaster’s leadership of the National Security Council staff has helped my administration accomplish great things to bolster America’s national security. He helped develop our America First National Security Strategy, revitalize our alliances in the Middle East, smash ISIS, bring North Korea to the table, and strengthen our nation’s prosperity,” Mr Trump said in a statement.

The President said on Twitter that an official handover would occur in April.

“I am thankful to President Donald J. Trump for the opportunity to serve him and our nation as national security advisor. I am grateful for the friendship and support of the members of the National Security Council who worked together to provide the President with the best options to protect and advance our national interests”, Mr McMaster said in a statement.

Mr Trump's initial pick for the role, General Michael Flynn, stepped aside after it emerged he had misled officials about conversations with the then-Russian ambassador; Mr Flynn subsequently pleaded guilty to lying to FBI agents who were investigating potential coordination between the Russian government and the Trump presidential campaign.

North Korea Military Parade Show all 6 1 /6 North Korea Military Parade North Korea Military Parade In this image made from video released by KRT on Feb. 8, 2018, a military parade is held at Kim Il Sung Square in Pyongyang, Thursday, Feb. 8 2018, just one day before South Korea holds the opening ceremony for the Pyeongchang Winter Olympics. (KRT via AP Photo) AP North Korea Military Parade This screen grab taken from North Korea's KCTV on February 8, 2018 shows members of North Korea's military taking part in a parade, with missiles being displayed, in Kim Il Sung Square in Pyongyang. North Korea staged a military parade in Pyongyang on February 8 to mark the 70th anniversary of its armed forces, in a show of strength just a day before the Pyeongchang 2018 Winter Olympic Games open in the South. / AFP PHOTO / KCTV / KCTV / -----EDITORS NOTE --- RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / KCTV" - NO MARKETING - NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS - NO ARCHIVESKCTV/AFP/Getty Images AFP/Getty Images North Korea Military Parade In this image made from video released by KRT, North Korean soldiers march during a military parade in Pyongyang, Thursday, Feb. 8 2018. North Korea held a military parade and rally on Kim Il Sung Square on Thursday, just one day before South Korea holds the opening ceremony for the Pyeongchang Winter Olympics. (KRT via AP Photo) AP North Korea Military Parade In this image made from video released by KRT on Feb. 8, 2018, North Korean leader Kim Jong Un, right, inspects honor guards, along with his wife Ri Sol Ju, center, during a military parade in Pyongyang, Thursday, Feb. 8 2018. North Korea held a military parade and rally on Kim Il Sung Square on Thursday, just one day before South Korea holds the opening ceremony for the Pyeongchang Winter Olympics. (KRT via AP Photo) AP North Korea Military Parade In this image made from video released by KRT on Feb. 8, 2018, North Korean leader Kim Jong Un, center, watches the military parade in Pyongyang, Thursday, Feb. 8 2018. North Korea held a military parade and rally on Kim Il Sung Square on Thursday, just one day before South Korea holds the opening ceremony for the Pyeongchang Winter Olympics. (KRT via AP Photo) AP North Korea Military Parade This screen grab taken from North Korea's KCTV on February 8, 2018 shows North Korean leader Kim Jong Un speaking during a military parade in Kim Il Sung Square in Pyongyang. North Korea staged a military parade in Pyongyang on February 8 to mark the 70th anniversary of its armed forces, in a show of strength just a day before the Pyeongchang 2018 Winter Olympic Games open in the South. / AFP PHOTO / KCTV / KCTV / -----EDITORS NOTE --- RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / KCTV" - NO MARKETING - NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS - NO ARCHIVESKCTV/AFP/Getty Images AFP/Getty Images

In elevating Mr Bolton, a staunch proponent of the Iraq war, the President has chosen an aide whose support for military entanglements abroad would seem to clash with Mr Trump's “America First” instincts and campaign promises to emphasise domestic issues.

The change also comes at a key moment for the Trump administration's foreign policy after the President committed to what would be an unprecedented meeting with North Korean leader Kim Jong-un to discuss denuclearisation.

In an interview with Fox News, Mr Bolton called the appointment “a great honour.”

“I’ve never been shy about what my views are, but frankly what I have said...is behind me, at least effective 9 April”, Mr Bolton said. “The important thing is what the President says and what advice I would give him”.

A hawkish figure who rose to prominence under George W Bush and a vocal supporter of the American invasion of Iraq, Mr Bolton served in the State Department during Mr Bush’s first term before becoming America’s ambassador to the United Nations.

Critics called the ambassador post an inappropriate choice given Mr Bolton’s history of assailing the international body, and Democrats later helped force his resignation by blocking a confirmation vote.

Mr Bolton has also been a fierce critic of Iran and North Korea, two countries that Mr Trump has forcefully criticised and that will likely continue to feature prominently in the Trump administration’s global posture.

In 2003, when he was serving as America’s chief arms control diplomat, Mr Bolton delivered a speech in Seoul, South Korea, denouncing then-North Korean leader Kim Jong Il as “a tyrannical dictator” whose country resembled a “hellish nightmare”.

The President is no stranger to using vivid language to denounce North Korea, threatening the regime of Kim Jong-un with military force as the country menaced neighbours and tested multiple intercontinental ballistic missiles in recent months.

But Mr Trump has also embraced a diplomatic opening with his extraordinary agreement to meet with Mr Kim. His openness to negotiating an end to North Korea's nuclear programme contrasts with Mr Bolton's repeated recent declarations that diplomatic approaches to North Korea cannot succeed.

In late February, shortly before the White House announced Mr Trump had accepted Mr Kim’s offer to meet, Mr Bolton wrote an op-ed backing a preemptive military strike on North Korea.

Sarah Sanders says HR McMaster will continue to do his job as Trump's National Security Advisor

Mr Bolton also shares Mr Trump’s suspicion of Iran, a country the President has singled out as a threat to the United States.

Mr Trump has frequently excoriated a deal forged during the Obama administration to halt Iran’s nuclear programme.

Warning Mr Obama’s approach towards Iran “has brought a bad situation to the brink of catastrophe”, Mr Bolton in 2015 authored an op-ed advocating a military strike on Iran’s nuclear facilities.

“The inescapable conclusion is that Iran will not negotiate away its nuclear program. Nor will sanctions block its building a broad and deep weapons infrastructure”, Mr Bolton wrote, saying that “only military action” can “accomplish what is required”.

That background prompted an outcry from Democrats in response to Mr Trump's selection of Mr Bolton. Rep Brendan Boyle of Pennsylvania called him a "dangerous radical" with a record of "undermining key alliances around the world", and several lawmakers said he had been discredited by his support for the Iraq war.