Special counsel Robert Mueller told President Donald Trump's lawyers last month that the U.S. leader is a subject of the investigation into Russian interference into the 2016 election, but he is not a criminal target at this point, The Washington Post reported Tuesday.

The Post, citing three sources, said the discussion took place during private negotiations early last month about a possible interview with Trump.

Additionally, the newspaper reported that Mueller told the president's lawyers he is readying "a report about the president's actions while in office and potential obstruction of justice."

The Post also cited legal experts who said that the president still could become a target of the investigation – particularly if investigators get the necessary information from Trump during a potential interview.

Here's how the Justice Department defines the difference between a "subject" and a "target" of an investigation:

A "target" is a person as to whom the prosecutor or the grand jury has substantial evidence linking him or her to the commission of a crime and who, in the judgment of the prosecutor, is a putative defendant. An officer or employee of an organization which is a target is not automatically considered a target even if such officer's or employee's conduct contributed to the commission of the crime by the target organization. The same lack of automatic target status holds true for organizations which employ, or employed, an officer or employee who is a target. A "subject" of an investigation is a person whose conduct is within the scope of the grand jury's investigation.

Trump has said publicly that he would talk to Mueller for the probe. According to various media reports, however, the potential for Mueller's team interviewing the president created friction within Trump's legal team. Last month, lead counsel John Dowd resigned from the team. Reportedly, he was opposed the idea of Trump talking to Mueller's team.

Mueller took over the investigation into Russian meddling in the 2016 election and potential links between the Trump campaign and the Kremlin in May 2017. Deputy Attorney General Rod Rosenstein appointed Mueller, a former FBI director, as special counsel after Trump fired FBI Director James Comey. In an interview with NBC News, Trump said Russia was one of the things on his mind when he decided to fire Comey.

White House lawyer Ty Cobb declined to comment to CNBC. A representative for the special counsel's office also declined to comment.

For more on this story, see the full report in The Washington Post.