Reporting by Paula Reid and Jacqueline Alemany

President Trump wants his attorney general, Jeff Sessions, to figure out who is behind a scathing anonymous New York Times op-ed, which described a "resistance" operating within the Trump administration, defying his worst impulses and desires.

"It's national security," the president said on Air Force One, on the way to a rally in North Dakota Friday. "I would say that Jeff should be investigating who the author of that piece was, because I really believe it's national security."

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The Justice Department issued a response to the president's Air Force One remark, saying in a statement, "The department does not confirm, deny or otherwise acknowledge the existence or non-existence of investigations."

The New York Times issued a statement saying, "We're confident that the Department of Justice understands that the First Amendment protects all American citizens and that it would not participate in such a blatant abuse of government power. The president's threats both underscore why we must safeguard the identity of the writer of this op-ed and serve as a reminder of the importance of a free and independent press to American democracy."

The president also said of the op-ed writer, "We're going to take a look at what he had, what he gave, what he's talking about, also where he is right now."

He offered another reason he wanted to know the identity of the author. "Supposing I have a high level national security, and he has got a clearance, we talked about clearances a lot recently, and he goes into a high-level meeting concerning China or Russia or North Korea or something," he said. "I don't want him in those meetings."

Asked whether any action should be taken against the Times, Mr. Trump responded, "I'm looking at that right now. It only happened yesterday."

Several Cabinet officials and agencies issued statements denying authorship of the op-ed. The Justice Department is one of the few that has not issued such a statement.

During an interview that aired early Friday on "Fox & Friends," Mr. Trump expressed frustration about the op-ed, calling it "unfair."

"What's unfair, I don't mind when they write a book and they make lies because it gets discredited," Mr. Trump said, but it's more difficult "when somebody writes and you can't discredit because you have no idea who they are."

Mr. Trump gave no indication that he was close to identifying the author but speculated that it "may be a deep state person who's been there a long time" or perhaps one of many, many people who can be designated as a senior administration official, which is how the person was identified in the Times op-ed.

"So they take one person out of thousands," the president told Fox News.

Steven Portnoy contributed to this report.