US President Donald Trump on Monday named Lieutenant General Herbert Raymond McMaster as his new national security adviser, choosing a military officer known for speaking his mind and challenging his superiors.

McMaster is a highly regarded military tactician and strategic thinker, but his selection surprised some observers who wondered how the officer, whose Army career stalled at times for his questioning of authority, would deal with a White House that has not welcomed criticism.

"He is highly respected by everybody in the military and we're very honored to have him," Trump told reporters in West Palm Beach where he spent the weekend. "He's a man of tremendous talent and tremendous experience."

One subject on which Trump and McMaster could soon differ is Russia. McMaster shares the consensus view among the US national security establishment that Russia is a threat and an antagonist to the United States, while the man whom McMaster is replacing, retired Lieutenant General Michael Flynn, appeared to view it more as a potential geopolitical partner.

Trump in the past has expressed a willingness to engage with Russia more than his predecessor, Barack Obama.

Flynn was fired as national security adviser on Feb. 13 after reports emerged that he had misled Vice President Mike Pence about speaking to Russia's ambassador to the United States about US sanctions before Trump's inauguration.

The ouster, coming so early in Trump's administration, was another upset for a White House that has been hit by miscues, including the controversial rollout of a travel ban on people from seven Muslim-majority countries, since the Republican president took office on Jan. 20.

The national security adviser is an independent aide to the president and does not require confirmation by the US Senate. He has broad influence over foreign policy and attends National Security Council meetings along with the heads of the State Department, the Department of Defense and key security agencies.

Not afraid to question his boss

Republican Senator John McCain, chairman of the Senate Armed Services Committee and a frequent Trump critic, praised McMaster as an "outstanding" choice.

"I give President Trump great credit for this decision," McCain said in a statement.

A former US ambassador to Russia under Obama, Michael McFaul, a Democrat, praised McMaster on Twitter as "terrific" and said McMaster "will not be afraid to question his boss."

McMaster, who flew back to the Washington area from Florida with Trump on Air Force One, will remain on active military duty, the White House said.