DONALD Trump has announced another dramatic change of personnel at the White House, replacing H.R. McMaster as national security adviser with former UN Ambassador John Bolton.

The announcement comes two weeks after the sacking of US Secretary of State Rex Tillerson.

The US President took to Twitter this morning to announce his National Security Advisor General H.R. McMaster would be replaced in April by former US Ambassador to the United Nations John Bolton.

“I am pleased to announce that, effective 4/9/18, @AMBJohnBolton will be my new National Security Advisor,” President Trump wrote.

“I am very thankful for the service of General H.R. McMaster who has done an outstanding job & will always remain my friend.

“There will be an official contact handover on 4/9.”

A vocal advocate of the Iraq war, he has also advocated preemptive strikes against North Korea and war with Iran.

His appointment had been fiercely opposed by many within Trump’s inner circle, most notably the coterie of military officers who have experienced the brutality of war first hand.

McMaster, a three star army general, had been expected to move out of the White House and into a four star position.

Instead he will retire from public life.

“After thirty-four years of service to our nation, I am requesting retirement from the US Army effective this summer after which I will leave public service,” he said in a statement.

“Throughout my career it has been my greatest privilege to serve alongside extraordinary service members and dedicated civilians.” His departure comes as Trump faces a high stakes meeting with North Korean leader Kim Jong Un and weighs the future of a deal to curb Iran’s nuclear weapons, which now appears to be in grave peril.

The White House said McMaster’s exit had been under discussion for some time and stressed it was not due to any one incident.

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.

Bolton, who has advocated military force against Iran and North Korea, will become the third person to hold the position in 14 months.

He served as the US ambassador to the UN from 2005-2006 and as Under Secretary of State for Arms Control and International Security from 2001-2005.

Bolton has served in the Republican administrations of Ronald Reagan, George HW Bush and George W Bush, and served as a Bush lawyer during the 2000 Florida recount.

In a statement, the White House described him as “one of the strongest voices and experts on the full range of national security issues and challenges facing the country”.

Earlier this month, The Washington Post reported President Trump had decided to replace McMaster. Mr Bolton was named as one of his potential candidates.

This marks the 21st replacement of a senior White House to date.

Tension between Trump and McMaster has grown increasingly public. Last month, Trump took issue with McMaster’s characterisation of Russian meddling in the 2016 election after the national security adviser told the Munich Security Summit that interference was beyond dispute.

“General McMaster forgot to say that the results of the 2016 election were not impacted or changed by the Russians and that the only Collusion was between Russia and Crooked H, the DNC and the Dems,” Trump tweeted February 17, alluding to frequent GOP allegations of impropriety by Democrats and Hillary Clinton. Tillerson’s exit also forecast trouble for McMaster, who had aligned himself with the embattled secretary of state in seeking to soften some of Trump’s most dramatic foreign policy impulses.

McMaster told The New York Times last year that Trump’s unorthodox approach “has moved a lot of us out of our comfort zone, me included”.

President Trump announced his decision to fire Mr Tillerson on March 13.

“I’m really at a point where we’re getting very close to having the Cabinet and other things that I want,” Trump told reporters in the US after Tillerson was fired.

It’s understood Trump never personally gelled with McMaster and the president recently told White House Chief of Staff John Kelly that he wanted the National Security Advisor replaced, according to the Post.

The publication reported Trump has complained that McMaster, a three-star Army general, was too rigid and that his briefings went on too long and seemed irrelevant.

McMaster is Trump’s second national security adviser, succeeding Michael Flynn who was dismissed a year ago for misleading Vice President Mike Pence about his contacts with the Russian ambassador to the United States.

The news also comes after someone at the White House leaked that Trump was urged in briefing documents not to congratulate Russian President Vladimir Putin about his recent re-election win. Trump did it anyway.