US President Donald Trump made the announcement on Monday following meetings at his Florida Mar-a-Lago resort. Addressing reporters in Palm Beach, Trump called Lt. General Herbert Raymond McMaster a "man of tremendous talent and tremendous experience."

"He is highly respected by everyone in the military and we're very honored to have him," the president added. McMaster is a West Point graduate known as "H.R.," with a Ph.D. in US history from the University of North Carolina at Chapel Hill. He was listed as one of "Time" magazine's 100 most influential people in 2014.

The National Security Advisor is an independent aide to the president and does not require confirmation by the US Senate. 

In a White House statement issued late Monday, McMaster said he was honored to serve in his new role, adding, "The safety of the American people and the security of the American homeland are our top priorities."

Flynn resignation

McMaster's predecessor, Michael Flynn, was forced to step down last week after misleading Vice President Mike Pence about discussions he had held with the Russian ambassador to the US concerning American sanctions on Moscow.

Trump said in a news conference last Thursday that he was disappointed by how Flynn had treated Pence, but did not believe Flynn had done anything wrong by having the conversations.

'Very, very special' collaboration

Sitting alongside Trump on a couch at the president's so-called "winter White House," McMaster described his appointment as a "privilege." The Afghanistan veteran, also played key roles in the Iraq War and Gulf War, and is known for his criticism of the US military's involvement in the Vietnam War. His 1997 book "Dereliction of Duty" criticized the country's military and political leadership for poor leadership during the Vietnam War.

The 54-year-old will now work alongside acting National Security Adviser Keith Kellogg, a retired three-star general, in a "very, very special" collaboration, Trump said. All three declined, however, to answer any questions from reporters, including over whether McMaster would be allowed to hire his own staff.

Former Navy SEAL rejects job

Trump's appointment of the new National Security Adviser on Monday followed days of interviews with a handful of candidates, including John Bolton, who previously served as Washington's United Nations ambassador under Republican president George W. Bush.

Retired vice admiral and former Navy SEAL, Robert Harward, reportedly turned down Trump's offer of the post last week over concerns that he would not be able to bring in his own team to staff the National Security Council. Other reports said he was put off by apparent ongoing chaos in the White House.

'Not my presidents day'

Anti-Trump activists took advantage of the federal Presidents Day public holiday to hold demonstrations in Atlanta, Chicago, Los Angeles, Washington and other cities. There were rallies in front of Trump International Hotel and near Central Park in New York with about 10,000 people taking part, according to an unofficial police estimate.

ksb/msh (AP, AFP, dpa)