Donald Trump tapped respected Army lieutenant general H.R. McMaster as his national security advisor, hoping to course correct after his first pick resigned and his second turned down the vital post, AFP reports.

Trump announced the counterinsurgency strategist's appointment at his Florida estate Mar-a-Lago, ending a one-week search to replace Michael Flynn, who lasted less than a month on the job.

Flynn was forced to resign on February 13, after questionable contacts with the Russian government and revelations that he lied about them to the vice president and the FBI.

Trump scrambled to replace Flynn after retired vice admiral Robert Harward turned down the post, amid a wrangling over lower-level National Security Council appointments and a meandering Trump press conference.

The White House said that Trump "gave full authority for McMaster to hire whatever staff he sees fit."

The 54-year-old McMaster is known for his criticism of the U.S. military's handling of Vietnam War and his own service as a commander in northern Iraq in 2005.

A 1997 book he authored is pointedly titled "Dereliction of Duty: Lyndon Johnson, Robert McNamara, the Joint Chiefs of Staff and the Lies That Led to Vietnam."

His experience in Iraq's Tal Afar is likely to come in useful as U.S. and allied forces attempt to retake nearby Mosul from the Islamic State group.