Washington (CNN) President Donald Trump's lead lawyer, John Dowd, has resigned from the President's personal legal team handling the response to the Russia investigation.

"I love the President and wish him well," Dowd said in a statement to CNN.

Dowd, who has urged the President to cooperate with special counsel Robert Mueller's probe and resist attacking him publicly, resigned as his disagreements with Trump intensified and the President stepped up his attacks on the special counsel. His departure raises questions about the direction of Trump's legal strategy and could signal a more aggressive posture on Trump's part.

Just days before his resignation, Dowd said in a statement the investigation should end, initially claiming he was speaking for the President before saying he was only speaking for himself. Two sources familiar with the matter said Trump had encouraged Dowd to speak out. But the statement only drew unwanted headlines and stoked turmoil within the President's legal team, according to multiple sources.

One source familiar with the decision described Dowd's resignation as a "mutual decision."

Despite public claims that he was happy with him, Trump complained privately in recent days that he thought Dowd was falling short of his duties, a source familiar with his thinking said. He questioned whether he had the energy or capacity to continue on in his role as the lead lawyer for the special counsel's investigation.

It was not immediately clear who would take over as the President's lead personal attorney, but Trump earlier this week hired another veteran Washington attorney, Joseph diGenova, to join his legal team. DiGenova was expected to play a forward-facing role on the legal team, filling what Trump felt was a lack of voices publicly defending him and challenging the special counsel.

DiGenova had publicly argued that Trump had been "framed" by FBI and Justice Department officials.

Dowd's departure also raises questions about the fate of negotiations between the President's attorneys and the special counsel's team over a potential interview with the President as Dowd has been the main point of contact with the special counsel's team throughout the investigation. One source said there is concern about the void Dowd will leave in his wake, particularly as Trump has had trouble finding top-flight lawyers to join his legal team.

Jay Sekulow, one of Trump's private attorneys, called Dowd a "friend" and said he "has been a valuable member of our legal team."

"We will continue our ongoing representation of the President and our cooperation with the Office of Special Counsel," Sekulow said in a statement.

As the investigation seems to be intensifying, the President, according to multiple sources, is convinced he needs to take the reins of his own legal strategy and Trump has recently pushed to bring new attorneys onto his team.

The shift distressed some of his lawyers, namely Dowd, who felt blindsided and insulted by the President's hire of diGenova and other shifts, privately threatening to quit before ultimately resigning on Thursday, two sources said.

Trump had also continued to speak regularly with Marc Kasowitz, his longtime lawyer who stepped back from leading the team months ago but still remained involved.

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Kasowitz had long recommended that Trump take a more aggressive posture toward the Mueller investigation. That strategy was on the backburner as Dowd and Ty Cobb, the White House's special counsel on the matter, worked with Mueller and urged the President to refrain from appearing to publicly undermine the Mueller investigation. Now that has all changed, as the President has reverted to his initial strategy to attack. An experienced cable news commentator, diGenova shares the President's view that the FBI and the Justice Department have waged a corrupt battle against him.

Dowd also faced criticism over his handling of the response to the guilty plea of Trump's former national security adviser Michael Flynn, who became the first Trump administration official to face charges in Mueller's investigation.

Dowd landed himself and the President in hot water after a tweet he says he authored suggested Trump knew Flynn lied to the FBI in January, reviving questions of whether Trump committed obstruction of justice when he allegedly asked then-FBI Director James Comey to drop the Flynn investigation.

"I had to fire General Flynn because he lied to the Vice President and the FBI. He has pled guilty to those lies," the tweet on Trump's account said.

The tweet led Sen. Dianne Feinstein, the top Democrat on the Senate Judiciary Committee, to note that the committee is investigating obstruction of justice and said: "What we're beginning to see is the putting together of a case of obstruction of justice."

In a testy exchange with CNN, Dowd said he authored the tweet, but then suggested it was incorrect, claiming that "at the time of the firing no one including Justice had accused Flynn of lying."

He declined to answer additional questions, saying: "Enough already ... I don't feed the haters."

The response was characteristic of Dowd's hard-charging style, which initially endeared him to the President and made him the lead attorney on the President's legal team after Kasowitz was asked to step back in July.

The latest shake-up now leaves questions about whether Trump's legal team will pursue the strategy that Dowd laid out in the wake of Flynn's guilty plea, when Dowd claimed that Trump could not be prosecuted for obstruction of justice because he is the US President and therefore its "chief law enforcement officer."

Dowd's claim signaled the President's legal team plans to rely on an untested theory that is heavily disputed by legal scholars: whether a sitting President can be charged with obstruction of justice or indicted at all.

CNN's John King and Kaitlan Collins contributed to this report.