WASHINGTON – In a pointed exchange during William Barr’s confirmation hearing earlier this week, Sen. Amy Klobuchar, D-Minn., engaged the nominee for attorney general in an ominous hypothetical:

If the president encouraged or instructed a witness to lie, would that act amount to obstruction of justice?

“Yes,” Barr said with little hesitation.

Two days after Barr’s appearance, the nominee’s spare response potentially takes on new meaning in wake of a disclosure that President Donald Trump allegedly instructed former personal attorney Michael Cohen to lie to Congress about the Trump Organization’s pursuit of a deal to build a luxury residential high-rise in the center of Moscow.

The Justice Department has long taken the position that a president cannot be prosecuted while in office, but Trump’s alleged direction to Cohen, as outlined in a report by BuzzFeed, has prompted Democrats to press for new congressional inquiries and has revived consideration of impeachment proceedings.

"As a counterintelligence concern of the greatest magnitude, and given that these alleged efforts were intended to interfere without our investigation, our committee is determined to get to the bottom of this and follow the evidence where it may lead," Rep. Adam Schiff, D-Calif., the new chairman of the House Intelligence Committee, said Friday.

Said former Obama administration Attorney General Eric Holder: “If true, and proof must be examined, Congress must begin impeachment proceedings."

USA TODAY has not confirmed BuzzFeed’s report.

Cohen, 52, who is expected to begin a three-year prison sentence in March after pleading guilty to federal financial crimes, campaign finance violations and lying to Congress, did not comment. Citing the ongoing investigation headed by Russia special counsel Robert Mueller, Cohen attorney Lanny Davis said that his client "declined to respond to the questions asked by the (BuzzFeed) reporters and so do I."

Later Friday, in an interview on MSNBC, Davis raised concerns about the security of Cohen's family in wake of his client's agreement to testify Feb. 7 before the House Oversight and Government Reform Committee. Davis said Cohen fears possible retribution from Trump allies, including those "abroad" in an indirect reference to Russia.

Because of those concerns, Davis said that Cohen's appearance is no longer certain. If he does appear, Cohen will not address questions about the BuzzFeed report, Davis said.

Trump, lashing out at the report via Twitter, took immediate aim at Cohen's credibility, and his family.

"Lying to reduce his jail time!" the president said Friday. "Watch father-in-law!"

Trump attorney Rudy Giuliani, meanwhile, called the BuzzFeed disclosures "categorically false."

The bitter recriminations offered by the president and his lawyer, however, only underscored the gravity of the new allegations and how they may relate to Mueller's inquiry into possible efforts by Trump to obstruct the investigation – and the parallel probe into possible coordination between the Trump campaign and Russia.

At the heart of new allegations is Cohen's involvement in the Trump Organization's pursuit of a Trump Tower project in Moscow and the subsequent efforts to conceal those actions during Trump's presidential bid.

Cohen lied when he told the Senate and House Intelligence Committees that all discussions about a Moscow development had ceased in January 2016, knowing that such efforts had continued through at least June – in the heat of the campaign and as Trump repeatedly denied any links to Russia.

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Prosecutors have asserted in court documents filed late last year that the tower project "likely required the assistance of the Russian government. And if completed, the company stood to gain hundreds of millions dollars from Russian sources in licensing fees and other revenues."

The court documents did not address whether Cohen's false statements about the Moscow tower discussions were prompted by any other consideration than an attempt to personally shield the campaign from public association with Russia.

The BuzzFeed report, however, not only asserts that Trump instructed Cohen to lie about the Moscow negotiations, but that documents seized by Mueller's investigators support the claim.

"If these allegations can be proven, (Trump) is toast, but only if the information can be corroborated," said Bruce Udolf, a former federal prosecutor who served as an associate independent counsel during the Whitewater investigation during the Clinton administration.

"Cohen's credibility is going to be attacked mercilessly, but that's already been happening," Udolf said.

Renato Mariotti, a former federal prosecutor in Chicago, said there was "no question" that directing a witness to lie to Congress is a crime. The stakes for Trump, Mariotti said, rise even higher because the allegation, if true, represents an act that few might dismiss.

"I think that everyone would probably agree that a president can never obstruct justice," Mariotti said.

Emerging in the midst of Barr's anticipated confirmation, the allegations promise to ratchet up the pressure on the Justice Department as it transitions to new leadership from ousted Attorney General Jeff Sessions, who Trump repeatedly accused of failing to shield him from the Russia inquiry.

"He (Barr) is walking into a pressure-cooker to begin with," Udolf said. "He only has to look back at what happened to the last guy to hold the office."

Giuliani, meanwhile, continued to hammer away at Cohen's credibility.

"Michael Cohen is a convicted criminal and a liar," Giuliani said in a statement. "To quote the prosecutors, he has traded on 'a pattern of lies and dishonesty over an extended period of time.' Today’s claims are just more made-up lies born of Michael Cohen’s malice and desperation, in an effort to reduce his sentence."