Mr. Trump appeared particularly incensed at public reports about his rancorous phone conversations with foreign leaders, including telling the president of Mexico the he might send American troops to stop “bad hombres down there,” and berating the prime minister of Australia over an Obama-era deal to resettle refugees and then cutting the call short.
He also expressed frustration over leaks about federal surveillance that picked up pre-inaugural phone calls between the Russian ambassador and Michael T. Flynn, who resigned under pressure this week from his role as national security adviser.
The Justice Department declined to comment on Mr. Trump’s call or on whether it had opened an investigation.
Susan Hennessy, a scholar at the Brookings Institution in Washington and former intelligence agency lawyer who has written about leaks, said that Mr. Trump’s directive could send a chilling message.
“The fear is that these leak investigations will be used as a form of political retaliation” against people who may have exposed information that is personally embarrassing to Mr. Trump, she said. “We don’t want this to become a political witch hunt.”
During the news conference, Mr. Trump did not directly answer questions about the substance of other recent reports on private dealings his aides may have had with Russia. Instead, he reframed the question as a problem of leaks. He declared that the “leaks are real,” but denounced articles based on the leaked information as “fake news.”
The president also suggested that he thought the leaks were coming from officials in unspecified “agencies” or “probably from the Obama administration,” rather than “our new people.”
Mr. Trump’s disclosure that he called the Justice Department for an investigation suggested that a recent trend of cracking down on unauthorized disclosures with criminal charges may continue during his administration.
For most of American history, the government did not prosecute those suspected of leaking. From the founding of the country through the end of the 20th century, just one person was convicted of leaking, and he was later pardoned.
But starting during the George W. Bush administration and intensifying in the Barack Obama administration, the government has brought leak-related charges far more frequently. Depending on how they are counted, Mr. Obama oversaw nine or 10 leak-related cases, more than all previous presidents combined.
Still, Matt Miller, a former director of public affairs for the Justice Department in Mr. Obama’s first term, said none of those cases involved going after someone who had leaked information about embarrassing or inappropriate activity by a president or his immediate staff.
“There is a fundamental question here: Does the attorney general take direction from the president about what he investigates, or is he independent?” Mr. Miller said. “That has been a question since Trump started talking about prosecuting Hillary Clinton.”
Mr. Trump is not the first president to speak about criminal investigations into leaks. But comparable recent precedents came in a different context.
In 2012, for example, after a series of news articles and books appeared about Mr. Obama’s national security record, Republicans accused the White House of leaking to help Mr. Obama win re-election.
In response, Mr. Obama said at a news conference that it was “offensive” to say the information had come from his White House, and raised the possibility of prosecuting whoever was responsible.
“These are criminal acts when they release information like this,” Mr. Obama said, “and we will conduct thorough investigations, as we have in the past.”
The next day, Attorney General Eric H. Holder Jr. announced that he was appointing United States attorneys to take over two major leak cases, although the F.B.I. had already been working on them.
And in September 2003, amid furor over the leaking of the identity of a C.I.A. official, President George W. Bush said at a news conference that “if there is a leak out of my administration, I want to know who it is, and if the person has violated the law, the person will be taken care of.”
But Mr. Bush did not commission that leak investigation; the Justice Department had already opened it based on a referral by the C.I.A.
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