President Donald Trump on Thursday attacked former special counsel Robert Mueller while speaking to reporters outside the White House, calling him a "true never-Trumper" and saying that he never should've been tapped as special counsel.

"I think Mueller is a true never-Trumper," the president said.

Trump's comments came one day after Mueller's first public remarks on his nearly two-year Russia investigation. Mueller said on Wednesday that if his team "had confidence that he clearly did not commit a crime, we would have said so."

Mueller resigned as special counsel on Wednesday.

Earlier Thursday, Trump tweeted that he had "nothing to do with Russia helping me to get elected." But he walked back that statement while speaking to reporters shortly after the tweet, saying that "Russia did not help me get elected."

"I helped me get elected," Trump said. "Russia had nothing to do with it at all."

Responding to Trump's earlier tweet, George Conway, a conservative attorney, frequent Trump critic and husband of top White House adviser Kellyanne Conway, made note of Trump "finally" admitting that Russia sought to boost his candidacy.

"Well, that’s what the investigation was about," Conway wrote. "The investigation found plenty of evidence that Russia did just that. It thus wasn’t a 'Witch Hunt' or 'Hoax.' So why did you repeatedly try to obstruct it?"

In Mueller's 400-plus page report on Russian interference in the 2016 presidential election and possible obstruction of justice by the president, he detailed Russia's extensive efforts to boost Trump's candidacy and harm 2016 Democratic presidential nominee Hillary Clinton through social media campaigns and by targeted email hacking and releases.

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Mueller documented multiple contacts between Trump campaign officials and associates with Russians, but wrote that the evidence was not enough to establish a broader Trump-Russia conspiracy. On obstruction, Mueller wrote that "while this report does not conclude that the President committed a crime, it also does not exonerate him."

During his Wednesday statement, Mueller made clear that he was guided from the start of his probe by Justice Department rules barring the indictment of a sitting president. Mueller said longstanding Justice Department policy made it so "a president cannot be charged with a federal crime while he is in office."

"That is unconstitutional," Mueller said. "Charging the president with a crime was therefore not an option we could consider."

The method for charging and removing a president, he said, lies outside the criminal justice system, referring to the Constitution's provisions for impeaching and convicting a president, which some congressional Democrats took as a signal that the special counsel had now placed the ball in their court.

With talk in Congress of starting the process to remove the president ramping up after Mueller's statement, Trump called impeachment a "a dirty, filthy, disgusting word."

"It was high crimes and misdemeanors," Trump said Thursday. "There was no high crime or there was no misdemeanor ? How do you impeach based on that?"

The president also said he hopes that his efforts to investigate the investigators — how the probe against him got started and what was it based on — will be remembered as his "greatest achievement, exposing all this corruption." Attorney General William Barr is currently reviewing the origins of the Russia investigation and the inspector general is examining the conduct of the FBI.

On Thursday, Trump said he thought Mueller's statement was "the same as" Mueller's report. Trump also said he believed the special counsel was "certainly conflicted" because of a "business dispute" the president claimed he had with Mueller.

Trump has mentioned an alleged business dispute for years since Mueller was first tapped. According to Mueller's report, top Trump aides and advisers such as former White House Counsel Donald McGahn told Trump those perceived conflicts were "silly" and "not real." As The Washington Post reported last year, the "business dispute" involved Mueller asking for a refund of his dues when he resigned his membership in 2011 at Trump's Northern Virginia golf club.

Additionally, Trump told reporters Thursday that he would give a "big league" statement later in the day or Friday dealing with illegal border crossings.

"I'm not closing the borders, I'm doing something else," the president said.