WASHINGTON – President Donald Trump denounced Russia special counsel Robert Mueller as a "rogue" prosecutor on Tuesday, a day after Mueller's office said that ex-Trump campaign chairman Paul Manafort has lied repeatedly to the FBI and violated a plea agreement.

"The Phony Witch Hunt continues, but Mueller and his gang of Angry Dems are only looking at one side, not the other," Trump tweeted. "Wait until it comes out how horribly & viciously they are treating people, ruining lives for them refusing to lie."

He added that "Mueller is a conflicted prosecutor gone rogue...:"

Prosecutors have also looked at whether Trump knew about Russian efforts to influence the 2016 election by hacking Democratic emails and pushing fake news about Democratic candidate Hillary Clinton, and whether the president has tried to obstruct the investigation.

Trump has denied both collusion and obstruction, and denounced the investigation as a politically motivated "witch hunt."

Democratic lawmakers say Manafort is a key witness, and that they are concerned that Trump may be weighing a pardon of his former campaign manager to keep him quiet.

Trump has never ruled out the idea of a pardon for Manafort or others who have been prosecuted by Mueller's team.

"After trying to tamper with witnesses and getting caught, Manafort should have learned not to mess with Robert Mueller," tweeted Rep. Adam Schiff of California, top Democrat on the House Intelligence Committee. "Apparently he did not."

After his conviction on financial fraud charges, Manafort struck a deal to cooperate with Mueller's team in September. The former campaign chairman met with prosecutors who have been looking into Russia's interference in the 2016 election.

One likely avenue of inquiry: Manafort's involvement in a 2016 meeting at Trump Tower of top campaign advisers and a Russian attorney promising damaging information on Clinton.

In a filing Monday, Mueller's team said it will soon provide "a detailed sentencing submission" on Manafort "that sets forth the nature of the defendant’s crimes and lies, including those after signing the plea agreement herein."

In the filing, Manafort's lawyers said he has lived up to the agreement.

Manafort "believes he has provided truthful information and does not agree with the government’s characterization or that he has breached the agreement," defense attorneys said.

In his tweets Tuesday, Trump also assailed the media for portraying Mueller as "a Saint," even though "he is doing TREMENDOUS damage to our Criminal Justice System."