US President Donald Trump has enthused about the well-tailored appearance of his new national security adviser, Robert C. O'Brien, The New York Times reported Wednesday.

The president was widely reported to have complained about the bushy mustache of O'Brien's immediate predecessor in the role, John Bolton.

Trump is known to be fixated with how his presidency plays out on TV, keenly monitoring how his aides perform in media interviews.

O'Brien previously worked as an attorney, as a diplomat, and as the White House's hostage negotiator. He was dispatched to Sweden recently to help secure the release of the American rapper A$AP Rocky, who had been arrested.

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For US President Donald Trump, glittering résumés and decades of experience aren't the only relevant factors when hiring officials to top positions — appearance counts.

Appearance is said to be something Trump's new hire as national security adviser, Robert C. O'Brien, had in his favor. A source close to the president told The New York Times in an article published Wednesday that Trump had enthused about O'Brien's well-tailored appearance and easy demeanor.

Trump had remarked that O'Brien "looks the part," The Times said, and contrasted him with his immediate predecessor in the role, John Bolton, whose bushy mustache and prickly personality were widely reported to clash with Trump's vision of a White House in which everyone looks as if they are straight out of "central casting."

Read more: The internet is blowing up with bewildered reactions and memes about Trump's abrupt firing of national security adviser John Bolton

John Bolton's thick mustache was the subject of presidential ridicule. Andrew Harnik/AP

Having been a reality-TV star before entering politics, Trump is known to be obsessed with how his presidency plays out on TV and to keenly monitor the media appearances of top advisers, sometimes watching them with the sound off.

At the outset of his presidency, Trump reportedly told advisers to consider each day of his presidency as like an episode in an unfolding television show in which he "vanquishes rivals."

In the early days of his presidency, he boasted that generals he had appointed to key national security roles looked as if they were from "central casting" — a key term of praise in the president's lexicon.

Read more: Meet Robert C. O'Brien, Trump's new national security adviser and a former hostage negotiator who monitored A$AP Rocky's trial in Sweden

According to Bob Woodward's book "Fear," which looks at the internal workings of the Trump White House, the president has in the past wavered on appointing key officials because he didn't like their appearance.

In one incident, Trump remarked that his second national security adviser, HR McMaster, looked like a "beer salesman," according to the book.

President Donald Trump once reportedly remarked that H.R. McMaster, his second national security adviser, looked like a "beer salesman." AP

Appearance aside, critics have questioned whether O'Brien, who previously served as the White House's top hostage negotiator, has enough government experience for the national security adviser role.

An attorney from Los Angeles, O'Brien got the president's attention by helping negotiate the release of two US captives abroad, and in August the president dispatched him to Sweden to negotiate the release of the rapper A$AP Rocky, who was being held on assault charges.

"I think the greatest challenge he will have is his relative lack of experience inside the US government, and with the interagency process, given that a gigantic part of the job is coordinating the interagency process," Richard Fontaine, the CEO of the nonpartisan Center for a New American Security, told The Times.