“He certainly doesn’t want to lay out his game plan for our enemies,” Ms. Sanders declared.

Sometimes, though, Mr. Trump’s statements leave his own staff in the dark, forcing them to impute a meaning to his words that might not actually exist. Privately, a few aides said they did not believe the president was preparing the country for war with either North Korea or Iran.

But they also noted Ms. Sanders has had a more successful debut as press secretary than her predecessor, Sean Spicer, in part because she has not attempted to clean up Mr. Trump’s statements – something that would rankle the president.

The president’s penchant for provocative statements is well established. In March, Mr. Trump tweeted, “Terrible! Just found out that Obama had my ‘wires tapped’ in Trump Tower just before the victory. Nothing found. This is McCarthyism!” The Justice Department later said there was no evidence that Mr. Obama tapped his apartment during the 2016 campaign.

Pressed by reporters at the time, Mr. Spicer tried to walk back the claim, saying “the president used the word wiretaps in quotes to mean, broadly, surveillance and other activities.”

Mr. Trump also shows an obvious delight in keeping people guessing. At the United Nations last month, he announced he had made up his mind about how to handle the Iran nuclear deal, but was not going to tell the public. When he met Prime Minister Theresa May of Britain, perhaps America’s closest ally, she asked him what he had decided. He refused to tell her, either.

“I didn’t know he was going to say today he’s made a decision,” a bemused Secretary of State Rex W. Tillerson said at the time. “I knew he had, but I didn’t know he was going to say he had.”