Secretary of Defense Jim Mattis walks to greet incoming national security adviser John Bolton upon Bolton's arrival for a meeting at the Pentagon, on March 29, 2018 in Arlington, Virginia | Mark Wilson/Getty Images Mattis jokes that he’s heard Bolton is the ‘devil incarnate’ President Donald Trump announced earlier this month that Bolton would be the new White House national security adviser.

WASHINGTON — Defense Secretary James Mattis joked Thursday that he’s heard new White House National Security Adviser John Bolton is “the devil incarnate” as the two men met for the first time outside the Pentagon.

“I’ve heard that you’re actually the devil incarnate and I wanted to meet you,” Mattis said as he and Bolton walked into the Pentagon past a pool of reporters.

President Donald Trump announced earlier this month that Bolton would replace H.R. McMaster as White House national security adviser, making Bolton the third person to serve in that role through the Trump administration’s 14 months. Bolton, a former U.S. ambassador to the United Nations under President George W. Bush and, more recently, a regular contributor to Fox News, is known for his intensely hawkish views, especially on key international issues related to Iran and North Korea.

Bolton’s selection to be national security adviser was immediately controversial, stoking fears that his interventionist views might push the president closer to armed international conflict.

Mattis, a retired Marine Corps general, said publicly after the announcement of Bolton’s hiring that he has never met the former U.S. ambassador to the U.N. But the defense secretary said he has “no reservations” and “no concerns at all” about working with Bolton.

“Last time I checked, he’s an American and I can work with an American. OK?” Mattis said earlier this week, according to Reuters. “I’m not the least bit concerned with that sort of thing.”