President Trump called Friday for the Justice Department to investigate the author of an op-ed depicting a “resistance” inside the government, as the White House mounted an all-out campaign to root out and discredit the anonymous senior official.

Speaking to reporters, Trump warned of a national security imperative to unmasking and punishing the person responsible for the New York Times piece depicting a “two-track presidency” in which some top staffers make up a “resistance” force working to thwart Trump’s “misguided impulses.”

“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,” Trump said during a flight from Billings, Mont., to Fargo, N.D., on a fundraising trip for Republican candidates. If the anonymous author has a high-level security clearance, the president emphasized, “and he goes into a high-level meeting concerning China or Russia or North Korea or something, I don’t want him in those meetings.”

Trump’s comments came at the end of a tumultuous week for the White House and on a day when he was eager to engage on a range of topics, seemingly testing which ideas could help him generate headlines and divert attention from questions raised in recent days about whether he is firmly in control of his administration. Along with floating a possible investigation into the author of the op-ed, Trump threatened to escalate his trade war with China, revealed he has been sent what he expects to be a “positive” letter from North Korean leader Kim Jong Un and said shutting down the government over funding for his wall along the U.S.-Mexico border could be a “great political issue.”

But the president’s growing paranoia this week over whether he can trust his underlings was most evident, coming after the back-to-back revelations in the Times’s op-ed and a new book from journalist Bob Woodward filled with anecdotes of senior aides working to set guardrails by withholding information from Trump or ignoring his requests, over purported fears of his competence.

On Friday, senior White House aides and Cabinet officials continued to rush out public denials of some of the allegations and eschew ownership of the op-ed. In her own op-ed in The Washington Post, U.N. Ambassador Nikki Haley called the anonymous author’s aims “very dangerous,” because they would sow “mistrust among the thousands of government workers who do their jobs honestly every day.”

Asked on the plane if he trusts his White House staffers, Trump said, “I do, but what I do now is I look around the room. I say, ‘Hey, if I don’t know somebody . . . ’ ”

Experts said it was unlikely the Justice Department would have sound legal grounds to get involved over a hunt for the op-ed author, unless the person was a member of the military, who are forbidden to undermine or defame the commander in chief.

But Trump’s preoccupation with the matter threatened to thrust him further into his ever-deepening war against the press corps at a perilous time. It also helped overshadow the release Friday of more positive economic news, which the president complains does not get more widespread attention amid the constant controversies around the White House.

The Labor Department reported Friday morning that August was the 95th straight month that the U.S. economy added jobs, with a robust 201,000 position gains. The new data also show that worker pay is on the rise, an encouraging sign that wages may finally be moving higher after years of sluggish progress.

“This is not called a recovery, this is called a rocket ship,” Trump said at a fundraiser in Fargo, N.D. “Job numbers were great.”

But Trump also told reporters that he was poised to dramatically escalate a trade war with China — implementing tariffs on an additional $267 billion in Chinese goods — that economists said could potentially affect the U.S. economy if a deal is not worked out with the world’s second-largest economy.

And Trump said he was expecting to receive a letter in the coming days from Kim, which would be delivered through Secretary of State Mike Pompeo. Two weeks ago, the president called off a trip to Pyongyang by Pompeo, citing a lack of progress in the nuclear disarmament talks. Trump noted that Kim said this week that he trusts Trump and hoped to achieve the denuclearization of the Korean Peninsula while he is in office.

“There’s never been a more positive statement,” Trump told reporters.

All of this comes as the president enters an accelerated campaign schedule in a bid to maintain GOP control of Congress. White House aides said he will be doing multiple campaign trips each week ahead of the Nov. 6 midterm elections, including stops next week in Missouri and Mississippi.

Adding to Trump’s list of heavyweight opponents, former president Barack Obama delivered a speech in Illinois on Friday that eviscerated Trump by name over their clashing worldviews, putting the current president on notice that his predecessor has shed his restrained public profile in a bid to directly engage him.

“It did not start with Donald Trump. He is a symptom, not the cause,” Obama said, calling on Democrats to get out the vote. “He is just capitalizing on resentments our politicians have fanned for years. . . . Appealing to tribe, appealing to fear. That’s an old playbook, as old as time. And in a healthy democracy, it doesn’t work.”

Trump dismissed Obama’s speech, calling it boring.

“I watched it, but I fell asleep,” he said at the fundraiser in Fargo. “I found he’s very good. Very good for sleeping.”

Trump’s comment Friday that Attorney General Jeff Sessions should investigate who wrote the newspaper op-ed isn’t the first time he has demanded that the FBI or Justice Department look into a disclosure that is embarrassing to the White House.

In the early days of the administration, the president and some of his aides repeatedly pressed then-FBI Director James B. Comey and other law enforcement officials to investigate not just leaks of classified information but also disclosures of unclassified, nonsensitive information, according to people familiar with the discussions.

Federal law enforcement officials have responded privately to such requests in the past by explaining an important distinction: Disclosing classified information can be a crime worthy of investigation; disclosing nonprotected information usually is not a crime, and therefore would not be investigated by federal agents.

“There’s virtually no context in which this kind of op-ed comes within a mile of federal criminal law,” said Stephen I. Vladeck, a law professor at the University of Texas. “Everyone can agree that if they find out who did it, the author can be fired, but we should be careful about the line between things for which you can be fired and things for which the president can sic the Justice Department on you.”

In a statement, a New York Times spokeswoman said the paper is “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.”

Also on the presidential jet, Trump denied one of the more shocking anecdotes in Woodward’s new book, “Fear.” Woodward reported that Gary Cohn, then the White House’s chief economic adviser, plucked a letter off Trump’s desk that the president intended to sign that would have terminated the trade agreement between the United States and South Korea.

In his book, Woodward published a picture of the unsigned letter.

Woodward also reported that Cohn took another memo off Trump’s desk that, had the president signed it, would have initiated the process for the United States to withdraw from the North American Free Trade Agreement with Canada and Mexico.

But Trump lambasted Woodward’s account as a “phony story.”

“Gary Cohn, if he ever took a memo off my desk, I would have fired him in two seconds,” Trump said. He added that Woodward’s tome is a “big, fat ugly book with all the misquotes and all the lies.”

Nakamura and Rucker reported from Washington. Devlin Barrett, Matt Zapotosky and Heather Long contributed to this report.