US President Donald Trump is replacing his national security adviser H.R. McMaster with former UN ambassador John Bolton, continuing a personnel shake-up in the White House that some perceive is taking his foreign policy in a more hawkish direction.

"I am pleased to announce that, effective 4/9/18, @AmbJohnBolton will be my new National Security Advisor," Trump tweeted on Thursday afternoon.

"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."

The announcement followed his firing of Secretary of State Rex Tillerson through Twitter a little more than a week ago, replacing him with Mike Pompeo, the current chief of the Central Intelligence Agency.

Bolton will be Trump's third national security adviser since the president took office 14 months ago. Trump's first national security adviser, Michael Flynn, was dismissed after less than a month.

The moves show Trump is surrounding himself with advisers more likely to agree with his views and taking his foreign policy in a more hawkish direction, Reuters reported.

Bolton has been widely considered a hawk who has advocated using military force against North Korea and Iran. Trump's new pick is "injecting a hawkish foreign policy voice into his administration ahead of key decisions on Iran and North Korea", The Associated Press reported on Thursday.

Bolton's appointment has drawn concerns from some on the Capitol Hill and beyond.

"With the appointments of Mike Pompeo and John Bolton, @realDonaldTrump is successfully lining up his war cabinet," Democratic Senator Edward Markey tweeted on Thursday.

"Bolton played a key role in politicizing the intel that misled us into the Iraq War. We cannot let this extreme war hawk blunder us into another terrible conflict," he said.