Special Counsel Robert Mueller’s tough tactics with investigation targets and witnesses are fueling complaints about the probe from President Trump and his allies at a critical stage, as key cooperation efforts seem to break down.

Just this week, conservative author Jerome Corsi balked at a plea deal after complaining the Mueller team wanted him to admit to lying (which he claims he didn't do) only after he “couldn’t give them what they wanted.” He tweeted Wednesday he now plans to pursue a complaint against Mueller's team.

Further, Mueller's team has accused ex-Trump campaign chairman Paul Manafort of violating his plea deal by lying to investigators, amid reports his cooperation agreement was not panning out how prosecutors had hoped.

More information also has come to light about the nature of those Mueller-Manafort interactions, as it emerged Manafort's legal team has been briefing Trump's team about their discussions. The briefings reportedly fueled tensions with Mueller's investigators, though it was already known that the president's and Manafort's legal teams have a joint defense agreement, meaning they share information.

But through these briefings, Trump's team learned about Mueller's focused line of questioning.

Specifically, top prosecutor Andrew Weissmann has been pumping Manafort for information about the president, with a focus on the highly scrutinized meeting at Trump Tower in June 2016 with Russian lawyer Natalia Veselnitskaya, and whether Trump knew about it in advance.

Trump lawyer Rudy Giuliani said the president is very upset with how Manafort has been treated, saying they keep hammering him with the same questions apparently seeking different answers.

Manafort already was convicted on multiple counts of financial fraud over the summer in connection with work he completed in Ukraine as a political consultant. A subsequent deal in a related case was seen as an opening for Mueller's prosecutors to get new information, but that possibility seems to be diminishing.

In a court filing on Monday, Mueller, Weissmann and several other investigators accused Manafort of violating his plea deal, which was agreed upon in September.

“After signing the plea agreement, Manafort committed federal crimes by lying to the Federal Bureau of Investigation and the Special Counsel’s Office on a variety of subject matters, which constitute breaches of the agreement,” Mueller, Weissmann, Jeannie Rhee and Greg Andres wrote in a court filing Monday.

But Manafort’s attorneys say he believes he has provided “truthful information” and “does not agree with the government’s characterization or that he has breached the agreement.”

James Trusty, a former federal prosecutor and senior Justice Department official, noted a judge will ultimately decide whether Manafort violated his plea deal.

“The breach of a plea agreement is a spectacularly ugly moment for everyone involved,” Trusty, now a white-collar attorney at Ifrah Law, told Fox News. “If you are found by the judge by a preponderance of evidence to have breached the agreement, you lose every good thing in it, but you’re stuck with the bad.”

He added: “This is going to see daylight and be fully litigated, and then we can make an informed judgment whether Mueller’s team is asking him the same questions over and over, or pursuing a real investigation and being sidetracked by a liar.”

Regardless of how that dispute resolves, Mueller's tactics run the risk of shutting down witnesses like Corsi.

In Trump World, anger and resentment toward the probe into Russian meddling and potential collusion with Trump campaign associates in the 2016 election is only building, as seen in the president's incendiary tweet-storm on Tuesday saying the probe is "ruining lives." He added Wednesday, “While the disgusting Fake News is doing everything within their power not to report it that way, at least 3 major players are intimating that the Angry Mueller Gang of Dems is viciously telling witnesses to lie about facts & they will get relief. This is our Joseph McCarthy Era!”

Former U.S. attorney Joseph diGenova, a Trump ally, called Weissman “one of the most unethical prosecutors ever to be in the Justice Department.”

Weissmann has overseen controversial prosecutions in the past that ultimately resulted in dismissed convictions and allegations of prosecutorial misconduct.

Meanwhile, Corsi plans to reject a potential deal with Mueller involving a perjury plea. The crucial piece of information was that he purportedly notified Trump associate Roger Stone in August 2016 that WikiLeaks intended to release information damaging to Hillary Clinton’s presidential campaign.

But Corsi complained he was cornered by Mueller, blasting the probe in an interview with Fox News’ “Tucker Carlson Tonight.” He said he did not knowingly give prosecutors false information, claiming he forgot about emails shown to him during his first interview, noting they were among 60,000 contained on a laptop he provided to the special counsel’s office.

“The special counsel came in … and they actually sent me home and gave me an opportunity to review the emails,” Corsi said Tuesday. “When I came back, I amended the testimony to say that I now remember the email. The special counsel was happy with that until I couldn’t give them what they wanted, which was a connection that I had with [Julian] Assange—that they assumed I had, which I didn’t have.”

He added: “Now suddenly, they forgot they allowed me to amend my testimony and they’re going back to the mistake I made when I forgot the email.”

Corsi described the investigation as “a political witch hunt,” echoing the president’s long-standing sentiment of the probe, further describing his interviews with investigators as a “memory test.”

“They ask you a question, they have material they won’t show you, you’ve forgotten about it, and they say, ‘You just lied because this email you forgot about in 2016 proves your current memory is wrong,” Corsi said. “If you can’t give them what they’re looking for to fill their narrative, they blow you up and charge you with a crime.”

Mueller’s team has secured several guilty pleas related to making false statements to federal investigators as part of the probe.

But Trusty told Fox News that “does not suggest a particularly successful investigation.”

“It’s heavy on false statement charges, and that doesn’t suggest that it’s moving in the right direction for the prosecution,” Trusty said. “It doesn’t suggest to me that they’re making a lot of headway on the substance of their investigation which is Russian collusion.”

He added: “As an ex-prosecutor, false statements are very distant second place.”

Trusty also said that during the FBI’s investigation of Hillary Clinton’s private email server, investigators and former FBI Director James Comey “swore off ever pursuing false statements charges,” quoting a recent Justice Department inspector general report.

“Are there two sets of rules?” Trusty said. “It’s a fair question that someone in the FBI or Justice Department ought to answer at some point.”

DiGenova, who has informally advised the president throughout the probe, suggested that Mueller was running a “parallel Justice Department.”

“These threats to Dr. Corsi and to Paul Manafort are a manifestation of a fatally flawed constitutionally corrupt investigation,” diGenova said. He added: “If you’re a Democrat, you get off scot-free, with immunity, and are able to destroy evidence and ignore subpoenas. If you’re a Republican, you’re going to jail no matter what.”

Despite the drama with witnesses, speculation is widespread that Mueller has much more information than prior reports indicate and could be preparing to strike with more indictments.

The president submitted his written answers to Mueller’s questions in the probe last week, marking a major milestone in the investigation. His attorneys said that despite their serious issues with the probe, the president has provided “unprecedented cooperation.”

Fox News’ John Roberts, Jake Gibson, Samuel Chamberlain and Christopher Wallace contributed to this report.