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WASHINGTON — The Trump administration is taking new steps to plug leaks of classified information, and it has tripled the number of criminal investigations involving illegal disclosures, top officials announced Friday.

The officials — Attorney General Jeff Sessions and Director of National Intelligence Dan Coats — appeared at the Justice Department to discuss a stepped-up enforcement effort against what Sessions called a "staggering number of leaks" that undermine "the ability of our government to protect this country."

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Sessions said the FBI has created a new unit to handle leak cases. He said the Justice Department has received nearly as many criminal referrals about leaks in the first six months of 2017 as it did in the previous three years combined.

Sessions didn't provide a number of referrals, but he did say the Trump administration has tripled the number of investigations since the end of the Obama administration. The Obama administration prosecuted more leak cases than any other in history.

A senior intelligence official told NBC News there were "dozens" of pending leak cases.

"I have this warning for would-be leakers," Sessions said. "Don't do it."

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Sessions also disclosed that the Trump administration is reviewing policies around how it subpoenas news media records. Former Attorney General Eric Holder adopted the guidelines after the Justice Department in 2013 secretly seized the phone records of The Associated Press, provoking deep concerns about press freedom.

The Obama Justice Department agreed in 2015 that it would not do that again except in cases of national security emergency, and that it would give media organizations a change to fight any records demand in court.

"We respect the role that the press plays ... but it is not unlimited," Sessions said.

No mention was made of prosecuting journalists for publishing classified information, a notion that was floated and abandoned during the George W. Bush administration.

Coats said that in recent years there have been "some of the worst compromises of classified information in the nation's history," which have harmed national security.

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"We will not allow rogue anonymous sources with security clearances to sell out our country," he said. "If you improperly disclose classified information, we will find you."

The announcement came a day after The Washington Post published transcripts of classified conversations between President Trump and the leaders of Mexico and Australia, prompting criticism even from ardent Trump critics.

"There was no public interest served" by that leak, which will discourage candid conversations among the president and his foreign counterparts, said Ned Price, a former CIA official and NBC analyst.

But many Trump critics, Republicans and Democrats alike, have cheered a series of leaks of classified or sensitive information that have shed light on the evidence at issue in the investigation of whether the Trump campaign colluded with the Russian election interference effort.

For example, current and former U.S. officials have disclosed to various news media outlets, including NBC News, the existence of communications intercepts and other intelligence documenting contacts between Trump associates and Russians during the 2016 election campaign.

A leak of classified information also appeared to be a key factor in the firing of Michael Flynn, Trump's first national security adviser. The White House took no action after acting attorney general Sally Yates warned officials that Flynn had not told the truth about his conversations with the Russian ambassador. It was only after the Washington Post disclosed that the FBI had intercepted Flynn's communications with the Russian that Trump fired Flynn.

Trump himself has also — seemingly inadvertently — disclosed classified information. In a May Oval Office meeting, he gave Russian officials sensitive details about terrorism intelligence relating to ISIS, sources told NBC News.

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And last week, Trump confirmed the existence of a covert CIA program he had just ended that had been arming Syrian rebels. He complained that some of the arms had wound up in the hands of Al Qaeda militants, a secret that had only been whispered about.

The Trump administration has also been bedeviled by leaks about the internal workings of the White House that may be embarrassing but have nothing to do with classified information. Republican strategist Alex Conant, in a Politico article headlined "Why Trump's White House Won't Stop Leaking," wrote that the Trump White House is beset by competing loyalties, disparate power centers and deep disloyalty — all recipes for leaks.