Donald F. McGahn II, the White House counsel, had warned the president before that such a blanket policy could not be imposed on federal employees. But in order to placate an angry president who was convinced that the people around him had to be pressured into keeping his secrets, Mr. McGahn drew up a broad document barring White House officials from publicly disclosing what they heard and saw at work.

That nondisclosure agreement, presented by Mr. Priebus to the senior staff last April, did not specify any penalties — financial or otherwise — and was something that almost everyone around the president understood could not be enforced. But it was an early indication that Mr. Trump, who spent decades using pressure tactics and secrecy in his private life, wanted to do the same thing at the White House, breaking with tradition. He would push the obsession of many of his predecessors with damaging leaks to a new level…

When Mr. McGahn told Mr. Trump it would be difficult to bind federal employees to such an agreement, Mr. Trump pushed back, believing that its existence could act as a deterrent to would-be leakers, a person with direct knowledge of the discussions said.