Acting attorney general Matthew G. Whitaker at an event last week in New York. (Peter Foley/EPA-EFE/Shutterstock)

Acting attorney general Matthew G. Whitaker was notified in advance that President Trump’s former personal attorney would plead guilty Thursday to lying to Congress about a Moscow real estate project that Trump and his company pursued while he was running for president, a person familiar with the matter said.

The notification could strain relations between Whitaker and Trump, who reacted to the plea by accusing his former attorney, Michael Cohen, of lying to spare himself prison time.

As acting attorney general, Whitaker is the nominal supervisor of special counsel Robert S. Mueller III, who has been investigating Cohen and signed his plea Thursday.

That is important because as a legal commentator before he came to the Justice Department, Whitaker was highly critical of Mueller’s work, even suggesting an acting attorney general could stifle Mueller’s budget to shut down his probe. Democrats and others have called unsuccessfully for Whitaker to recuse himself from the case, in part because of his past comments, fearing he might take steps to interfere with the ongoing investigation.

Justice Department policies and special-counsel regulations call for Whitaker to be notified of significant events, including “major developments in significant investigations” and “events affecting the Department that are likely to generate national media or Congressional attention.”

Importantly, though, the regulations do not require the attorney general to approve such steps. The attorney general can request that the special counsel explain a step that is being taken and can conclude that an action is “so unwarranted under established Departmental practices that it should not be pursued.”

The attorney general is supposed to give “great weight” to the special counsel’s views, and at the end of the case Congress is supposed to be notified of any proposed action that was vetoed.

It was not immediately clear when the special counsel’s office notified Whitaker of Cohen’s plea, or how Whitaker reacted. Cohen’s appearance Thursday in federal court in Manhattan, at which he admitted lying about the Moscow project, surprised many in the media.

A Justice Department spokeswoman declined to comment.

Cohen admitted as a part of his plea that he lied in part to “minimize links” between the Moscow project and Trump, and in hopes of limiting ongoing probes into ties between Russia and the Trump campaign. Prosecutors said in court documents that he discussed efforts to obtain Russian assistance for the project as late as June 2016 and discussed the status and progress with Trump more than he had previously told congressional investigators.

Trump said his former attorney was “lying, and he’s trying to get a reduced sentence for things that have nothing to do with me.” The president also stressed that the project never came to fruition.

Trump replaced his attorney general, Jeff Sessions, with Whitaker in part because the president was frustrated that Sessions recused himself from the special-counsel probe and thus had not restricted it in any way. When Sessions was in place, Mueller was supervised by Deputy Attorney General Rod J. Rosenstein, who remains the Justice Department’s No. 2 official.

Whitaker was scheduled to speak in Nashville on Thursday afternoon about the opioid crisis.