Mr. Trump’s press secretary, Sean Spicer, has been open about wanting to expand the list of news outlets that traditionally have been regularly called on during White House briefings. He began his first briefing by calling on a reporter from The New York Post, Daniel Halper, who also got a question at Mr. Trump’s news conference on Friday with Prime Minister Shinzo Abe of Japan.

Mr. Spicer did not respond to a message seeking comment for this article.

Joint news conferences with the president and visiting foreign leaders are an awkward ritual, even during the best of times. First there is the simultaneous translation, during which both leaders need to wear earpieces, something that caught Mr. Trump off guard with Mr. Abe. He did not put in the earpiece during the prime minister’s lengthy introduction.

Normally, the leaders call on two reporters from each of their respective countries, ostensibly to ask both of them about their just-concluded meeting. In reality, reporters often seize the opportunity to quiz the president about the pressing news of the day, which often has nothing to do with, say, Canada or Japan.

Foreign leaders often find themselves standing uncomfortably while their host tangles with reporters about health care policy or other domestic issues. That is even truer for leaders from countries, like Canada and Japan, with which the United States has generally tranquil relations, and hence generate little in the way of juicy news.

On Friday, for example, Mr. Halper asked Mr. Trump about his reaction to the federal court ruling striking down his immigration order. The president, clearly not yet used to the drill, replied with palpable irritation: “Well, your question was unrelated to what we are here for today, but I will answer it. We are going to keep our country safe.”

On Monday, Mr. Trump got no such surprises. His first questioner, Scott Thuman of Sinclair Broadcast Group, asked the president how he expected his relationship with Mr. Trudeau to develop on issues like terrorism and immigration, given their “notable and philosophical differences.”