President Trump took to Twitter Thursday morning to deny one of the most explosive assertions in special counsel Robert Mueller's report — that the president instructed then-White House counsel Don McGahn to fire Mueller.

Mueller's report clearly asserts that in June 2017 the president directed the top White House lawyer to get rid of Mueller — twice. McGahn told the special counsel's team that the president called him on two occasions, telling him "Mueller has to go" and instructing him to inform Deputy Attorney General Rod Rosenstein of his decision. But McGahn, according to Mueller's report, felt uncomfortable, and instead prepared to resign, although the White House chief of staff at the time, Reince Priebus, and counselor Steve Bannon convinced him to stay. But the president insisted Thursday that wasn't the series of events.

"As has been incorrectly reported by the Fake News Media, I never told then White House Counsel Don McGahn to fire Robert Mueller, even though I had the legal right to do so. If I wanted to fire Mueller, I didn't need McGahn to do it, I could have done it myself," the president tweeted. Nevertheless ... Mueller was NOT fired and was respectfully allowed to finish his work on what I, and many others, say was an illegal investigation (there was no crime), headed by a Trump hater who was highly conflicted, and a group of 18 VERY ANGRY Democrats. DRAIN THE SWAMP!"

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McGahn has been subpoenaed to testify before the House Judiciary Committee, given his prominent role in Mueller's report, but the White House is stalling on the request. Mr. Trump says he doesn't want any current or former officials to testify before Congress. And a senior White House official tells CBS News that the "White House will keep all of its legal options open in regard to any subpoena served on a current or former administration official."

Mueller's report found that several top aides surrounding the president, including McGahn, on occasion saved the president from acting in ways that could have threatened his presidency.

"The president's efforts to influence the investigation were mostly unsuccessful, but that is largely because the persons who surrounded the president decline to carry out orders or accede to his requests," Mueller's report said.

It's unclear exactly if or how the White House could stop McGahn from testifying altogether, given that he's a former, not a current, White House employee. McGahn has not yet said whether he will comply with the subpoena.