President Donald Trump's attorney general nominee said this week that it would be a crime for the president to coach a witness to lie to investigators.

William Barr's statements have taken on a new significance in light of reporting that Trump directed his former lawyer, Michael Cohen, to lie to Congress when testifying before the House Intelligence Committee in 2017.

The special counsel Robert Mueller reportedly learned about Trump's instruction to Cohen through "multiple witnesses," documents, internal emails, and text messages from members of the Trump Organization, then from Cohen, who is now cooperating with prosecutors.

Mueller has already shown a willingness to charge individuals who were found to have misled congressional or FBI investigators.

Barr's confirmation that coaching a witness to lie constitutes a crime could foreshadow mounting legal peril for the president.

William Barr, President Donald Trump's nominee for attorney general, testified this week that if the president tried to convince witnesses not to testify in an investigation or to suborn perjury, it would constitute obstruction of justice.

Barr's comments, made during an exchange with Senate Judiciary Committee chairman Lindsey Graham, have taken on a new significance following a bombshell report from BuzzFeed News released Thursday, which alleges that Trump instructed his former lawyer, Michael Cohen, to lie to Congress about the now-defunct Trump Tower Moscow deal.

"If there was some reason to believe that the president tried to coach somebody not to testify, or to testify falsely, that could be obstruction of justice?" Graham asked Barr during his confirmation hearing Tuesday.

"Yes, under that — under an obstruction statute, yes," Barr replied.

"So if there's some evidence that the president tried to conceal evidence, that would be obstruction of justice, potentially?" Graham pressed.

"Right," Barr said.

The former attorney general sent a memo to the Justice Department and the White House, as well as lawyers representing other defendants in the ongoing Russia investigation, in which he said the special counsel Robert Mueller's obstruction-of-justice investigation was "legally insupportable."

Given Barr's broad and controversial view of executive power, his assertion that it would constitute obstruction if the president directed someone to lie to investigators is particularly noteworthy, and may foreshadow significant legal peril for Trump in light of BuzzFeed News' report.

The Trump Tower Moscow deal is a focus for Mueller and congressional investigators examining Russia's interference in the 2016 US election, and whether the Trump campaign secretly worked with Moscow to tilt the race in Trump's favor.

Cohen has admitted to lying to Congress about multiple aspects of the Trump Tower Moscow deal, including how long the Trump Organization pursued the deal, the extent of his communication with Russian government officials, and the involvement of multiple Trump family members in pushing the deal through.

Mueller reportedly learned about Trump's instruction to Cohen through "multiple witnesses," documents, internal emails, and text messages from members of the Trump Organization, then from Cohen himself — who is now cooperating with prosecutors.

Citing two law enforcement officials, BuzzFeed News reported that during the 2016 campaign Cohen had "at least 10 face-to-face meetings" with Trump about the Moscow deal, which Trump thought could bring in more than $300 million in profits for his company.

Cohen told Mueller that after Trump won the 2016 election, he instructed him to lie about when talks about that Moscow deal ended "in order to obscure Trump's involvement," the report said.