U.S. President Donald Trump is replacing national security adviser H.R. McMaster with former UN Ambassador John Bolton, an outspoken hawk who has advocated using military force against Iran and North Korea.
Trump tweeted late on March 22 that McMaster, 55, had done "an outstanding job and will always remain my friend," but he said Bolton will take over on April 9.
An advocate of "regime change" in Iran who served in the administrations of former Presidents Ronald Reagan, George H.W. Bush and George W. Bush, Bolton, 69, has been an especially strong critic of Iran's 2015 nuclear agreement with world powers.
Bolton recently tweeted that the deal "needs to be abrogated."
Trump campaigned against the deal and vowed to end it, but during his first year in office he heeded McMaster's advice to delay the move -- a cautious stance also take by ousted U.S. Secretary of State Rex Tillerson.
Since dismissing Tillerson last week and announcing his intent to replace him with more hawkish CIA Director Mike Pompeo, Trump has signaled he is eager to make good on his promises on Iran.
"You're gonna see what I do," Trump said on March 21, when asked about his plans on Iran.
Trump had originally considered choosing Bolton, a Fox News commentator, as his secretary of state. But many congressional Democrats object to Bolton and he might have had difficulty getting confirmed by the Senate.
"This is not a wise choice. Mr. Bolton does not have the temperament or judgment to be an effective national security adviser," Democratic Senator Jack Reed said after Trump announced his pick of Bolton.
The post of national security adviser is not a cabinet-level position, so Bolton will not need Senate approval to assume the job.
Bolton called his appointment "an honor" and said he looked "forward to working with President Trump and his leadership team" to "make our country safer at home and stronger abroad."
Bolton was a leading advocate for the 2003 U.S.-led invasion of Iraq during George W. Bush's administration, and as a commentator he has advocated taking preemptive military action against both Iran and North Korea.
AP reported that Bolton has met regularly with Trump at the White House, including having a meeting earlier this month with Trump and White House Chief of Staff John Kelly to discuss North Korea and Iran.
In replacing both McMaster and Tillerson, Trump has said he was seeking more like-minded aides. He had increasingly clashed publicly with McMaster, a respected three-star general who said he planned to retire from public life this summer.
Last month, Trump took issue with McMaster's characterization of alleged Russian meddling in the 2016 presidential 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," Trump tweeted.
Last summer, McMaster was the target of an attack ad campaign by conservative groups, which accused him of not being tough enough on Iran.
While Bolton's views on Iran are close to Trump's, he appears to have advocated a more hawkish stance toward Russia than Trump, who has said he wants to improve ties with Moscow.
Among other tweets, Bolton has called for "effective countermeasures to the cyberwar that Russia is engaging."
Bolton said in an interview with Fox News on March 22 that as Trump's security adviser, he will be an "honest broker" who presents multiple views for the president to consider.
"The important thing is what the president says and the advice I give him," he told Fox.
The human rights group Amnesty International on March 22 called Bolton's appointment "reckless."
"Bolton's influence over national security policy could result in even more civilian deaths and potentially unlawful killings given his disdain for international law and international institutions," said Zeke Johnson, senior director of programs at Amnesty International USA.