WASHINGTON — Former President Barack Obama personally cautioned President Donald Trump against hiring Michael Flynn, according to news reports Monday, as former acting U.S. Attorney General Sally Yates testified separately about warning the White House that the now-ousted national security adviser “could be blackmailed” by Russia.

Yates, appearing on Capitol Hill for the first time since Trump fired her over a separate matter, said she met twice in January with White House Counsel Donald McGahn to discuss “underlying conduct” by Flynn that was “problematic.”

“We were giving them this information so they could take action,” she said. “To state the obvious, you don’t want your national security adviser compromised with the Russians.”

Yates, who served 10 days under Trump as an Obama administration holdover, would not detail Flynn’s conduct because she said it involved classified information.

Multiple news outlets have reported that before Trump took office, Flynn discussed Obama-imposed sanctions against Russia with a Kremlin ambassador.

Meanwhile, just after Trump was elected, Obama advised against hiring Flynn during an Oval Office face-to-face with Trump, according to former Obama administration officials speaking anonymously to multiple news outlets.

White House press secretary Sean Spicer said Obama made it known that “he wasn’t exactly a fan of General Flynn’s.”

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But Spicer also asked why Obama didn’t suspend Flynn’s security clearance and why he “let” Flynn take a paid speaking spot with a Russian-sponsored news station a year earlier.

In a tweet, Trump doubled down on the blame of Obama.

“General Flynn was given the highest security clearance by the Obama Administration — but the Fake News seldom likes talking about that,” he posted.

Flynn, a retired Army lieutenant general, was Obama’s Defense Intelligence Agency director until he was fired in 2014.

He then was appointed as national security adviser to Trump but ousted because he misled Vice President Mike Pence over his communications with Russia.

Speaking before a Senate panel, Yates said it was Pence’s public statements unknowingly misrepresenting Flynn’s contacts with Russia that led her in part to warn the White House.

Yates said she met with McGahn on Jan. 26 and Jan. 27, and also spoke with him by phone on Jan. 27.

Trump asked for Flynn’s resignation 18 days later.

Spicer and White House Chief of Staff Reince Priebus had characterized Yates’ discussions with McGahn as a “heads-up.” Yates described the conversations as urgent on her part, saying she and McGahn talked about possible criminal prosecution of Flynn and why the Justice Department would care that one White House official would lie to another.

McGahn expressed concern that acting against Flynn would compromise an FBI investigation into his dealings, she said.

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Trump fired Yates for directing DOJ attorneys not to defend his executive order barring some travelers, including those from Muslim-majority countries.

Yates maintained Monday that she was doing her job in determining that the travel ban was unconstitutional.

The president indicated in a tweet that he believed Yates might be responsible for leaks of classified information.

“Ask Sally Yates, under oath, if she knows how classified information got into the newspapers soon after she explained it to W.H. Counsel,” Trump directed of senators.

Some did ask her whether she or someone who represented her had served as an anonymous source to reporters on investigations into Trump and Russia.

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Yates said no.

Former Director of National Intelligence James Clapper, also testifying, said no.

The president fired off several post-hearing tweets, noting that Clapper reiterated he had not seen evidence of collusion between Trump’s team and Russia, calling stories discussing possible cooperation a “taxpayer-funded charade” and saying he believed Yates revealed “nothing but old news.”