(H.R. McMaster.Thomson Reuters)

President Donald Trump has repeatedly clashed with his national security adviser, H.R. McMaster, in front of his staff, according to a column by Eli Lake at Bloomberg published Monday.

The three-star Army general increasingly is being sidelined in favor of other advisers because Trump has become "disillusioned" with him, according to Lake. Three White House officials told Lake the president was "livid" after McMaster called his South Korean counterpart to assure him that Trump's threat to make Seoul pay for the advanced THAAD missile defense system was not official policy.

Trump also has said in front of McMaster that he is "undermining my policy," according to two White House officials who spoke with Lake.

The White House did not immediately respond to a request for comment from Business Insider. However, Bloomberg received a statement from Trump that said: "I couldn't be happier with H.R. He's doing a terrific job."

McMaster received plenty of praise when he was tapped to replace retired Lt. Gen. Michael Flynn as national security adviser. Many pundits said his strategic expertise, doctoral education, heroism during Operation Desert Storm, and respect among the rank-and-file would be good news for Trump's National Security Council.

But as I noted in February, McMaster is not known to be a yes man, which may be rubbing Trump the wrong way:

"McMaster is the kind of guy who says what's on his mind and will call out a wrongheaded approach when he sees one. That tendency is something that junior officers love, but those maverick ways are not well-received by some of his fellow generals. Put simply: McMaster isn't a political guy, unlike other officers who are trying to jockey for position and move up in their careers.

"In 2003, for example, McMaster criticized then-Defense Secretary Donald Rumsfeld's Iraq War plan that placed too much of an emphasis on technology. McMaster also pushed back on his boss' refusal to admit an insurgency was starting to take hold in 2004.

"He has been held back in his career because of it — he was passed over two times for his first star — but it wasn't because of incompetence. Instead, his fight to be promoted from colonel to brigadier general was seen as pure politics, and McMaster doesn't like to play. He was eventually promoted in 2008, but that hasn't made him any less outspoken."

For now, McMaster's standing in the White House seems to be a "he said, she said" situation — though it's worth noting that the White House was publicly praising Flynn's performance hours before he was asked to resign.

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