ABOARD AIR FORCE ONE • US President Donald Trump has called for the Justice Department to probe the author of an op-ed depicting a "resistance" inside the government, as the White House mounted an all-out campaign to root out the anonymous senior official.

Speaking to reporters on Friday, Mr 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 staff make up a "resistance" force working to thwart Mr 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," Mr Trump said during a flight from Billings, Montana, to Fargo, North Dakota.

If the anonymous author has a high-level security clearance, the President emphasised, "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".

Mr 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.

Asked on the plane if he trusts his White House staff, Mr 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.

THE WASHINGTON POST