Secretary of Defense Jim Mattis called a report “fiction” that claimed the Pentagon was engaged in a “damage control” operation following Trump’s visit to NATO headquarters.

“That was fascinating. I love reading fiction,” Mattis said of the report, published by NBC. “So it was — it was stimulating to read it. I find out while I've been with you with full transparency on the airplane, you watching what's going on; that I've been in damage control.”

“I must tell you, it must have been the most pleasant damage control in the A-5 I ever could have imagined with the level of unity, of purpose that we experienced there,” he added. “So anyway, people are entitled to their own opinion, even if it's not fact-based.”

The comments come after NBC reported that Pentagon officials were working to restore confidence in “alliance commitments” following comments from Trump that “made it clear alliance commitments were on the table,” one U.S. official told NBC News.

Trump was critical of U.S. allies at the NATO summit in Brussels earlier this week during public remarks.

"Many countries are not paying what they should. And, frankly, many countries owe us a tremendous amount of money for many years back, where they're delinquent, as far as I'm concerned, because the United States has had to pay for them," Trump said of NATO allies Thursday.

"So if you go back 10 or 20 years, you'll just add it all up. It's massive amounts of money is owed," he added.

But despite the comments, French President Emmanuel Macron remained firm that Trump did not suggest he would pull out of NATO.

Mattis’ comments were made to the media while traveling to Oslo, Norway.