Rep. Devin Nunes said Robert Mueller could "throw a monkey wrench" into matters related to the Russia investigation with his testimony next month.

In an interview Saturday evening on Fox News, the California Republican also expressed concern about what one of Mueller's top prosecutors might say in a closed setting as part of the deal to speak to lawmakers.

"There are two trains of thought out there. One is that he’s just not going to say anything, which is very possible. But it’s also very possible too that he could throw a monkey wrench in things," the House Intelligence Committee ranking member told host Jeanine Pirro.

"Now what's off about this is — supposedly he's only agreed to testify for four hours. Four hours with the House Intelligence Committee and the House Judiciary Committee is not enough time to get everyone’s questions in," Nunes added. "In addition, people should know he’s not willing to testify as of now behind closed doors and he’s supposedly going to send in Andrew Weissmann and his team of geniuses that came up with these conspiracy theories. And that’s not even going to be translated. So stay tuned."

Mueller, who made clear in a public statement late last month he did not want to testify about his now-complete investigation, agreed to public testimony before the House Intelligence and Judiciary committees on July 17 in response to a pair of subpoenas.

In an interview with CNN last week, House Intelligence Chairman Adam Schiff said he did not believe the special counsel's office considered what it received to be a "friendly subpoena" and that Mueller was "deeply reluctant" to comply with it.

As part of the plan, Schiff said that there will also be an "executive session" with members of Mueller's staff.

There has been some speculation about what this closed-door discussion might entail.

Former FBI Deputy Director Andrew McCabe told MSNBC that Mueller's senior staffers will likely "go much deeper" into the details of the Russia investigation. Joe DiGenova, a former U.S. attorney for the District of Columbia, predicted on Fox Business last week that Weissmann, not Mueller, could do real "damage" to President Trump.

Weissmann, who recently scored a book deal, was known as Mueller's "pitbull." According to Michael Wolff's book Siege, Weissmann led the initiative to draft a three-count obstruction of justice indictment against Trump, which Mueller's spokesman denied existed.

Mueller's report, released in April with redactions, shows his team was not able to establish criminal conspiracy between the Russian government and the Trump campaign, but left open the question of possible obstruction of justice. The report laid out 10 instances in which Trump might have obstructed justice, but Mueller declined to make a determination on the matter, citing a Justice Department guideline that sitting presidents cannot be indicted.

Although Trump and his allies say the case is closed, Democrats argue Mueller's refusal to clear Trump on obstruction provides them a road map to continue to investigate and possibly seek impeachment. Attorney General William Barr said he and former Deputy Attorney General Rod Rosenstein determined there was not sufficient evidence to establish a crime had occurred.

Despite Mueller being out of the job and his reluctance to testify, Nunes complained of the former special counsel's continual presence. "He’s like a bad penny, he just won’t go away," Nunes said of Mueller.

Nunes said a question he wants to ask Mueller is how far the counterintelligence investigation into Trump's campaign goes, even as the FBI asserts it started in July 2016.

"That is a total lie. They've been lying to Congress. They've been misleading the American people, and I'm going to ask that question or at least me or somebody on my committee is going to ask that question of Bob Mueller when the investigation actually began spying on the Trump campaign," Nunes said.