President Trump’s frustration with the Russia probe boiled over in a fiery new interview where he set a red line for Special Counsel Robert Mueller, warning against digging into his family finances beyond the Russia scope and suggesting he’ll soon start talking about the ex-FBI director’s “conflicts.”

The president has regularly complained about the Russia meddling probe, before and after it was placed in the hands of the special counsel. But his comments to The New York Times indicate he’s preparing to get even more aggressive in challenging the credibility of the investigation.

Significantly, he said Mueller would cross a red line if he started looking at Trump family finances going beyond any Russia connection.

''I think that's a violation. Look, this is about Russia,” Trump said.

The interview leaves unclear under what circumstances, if any, he might order the Justice Department to fire Mueller. But he complained anew that the special counsel was hiring lawyers who donated to his general election rival Hillary Clinton and called him out for having interviewed for the job to replace ex-FBI Director James Comey just before his appointment.

TRUMP BLASTS SESSIONS FOR RECUSAL

''He was up here and he wanted the job,'' Trump told the Times.

The president said after Mueller was named, he said to himself, “'What the hell is this all about?' Talk about conflicts. But he was interviewing for the job. There were many other conflicts that I haven't said, but I will at some point.''

In the same interview, Trump also issued a remarkable denunciation of Attorney General Jeff Sessions, one of his earliest and staunchest supporters, for having recused himself in the Russia case.

"How do you take a job and then recuse yourself?" Trump asked rhetorically. "If he would have recused himself before the job, I would have said, 'Thanks, Jeff, but I’m not going to take you.'"

There was no immediate comment from Sessions, who announced March 2 that he would recuse himself from overseeing the FBI's investigation into alleged Russian meddling into the 2016 presidential election campaign. Sessions stepped aside after media reports that he had two conversations with Russia's ambassador to the U.S. and failed to disclose them to Congress during his confirmation process.

In a separate interview with Fox News’ Martha MacCallum on “The Story,” Deputy Attorney General Rod Rosenstein defended his selection of Mueller to lead the probe.

“I've got to explain that I made the decision to appoint Director Mueller based upon his reputation. He had an excellent reputation. Really bipartisan support for his integrity,” he said.

He added, “I think you have to keep in mind that the point of having a special counsel is to have some degree of independence from the Department of Justice. So Director Mueller's not reporting to me about individual decisions made in his investigation. … But it also provides some degree of insulation because what we want to be able to do, is at the end of the day, to be able to say that we appointed somebody who was independent, who made independent decisions, and therefore we can have confidence in the result that they reach.”

This is not the first time Trump has sounded off on the Mueller probe. He told “Fox & Friends” last month that Mueller’s friendship with Comey is “very bothersome.”

He added, “I can say that the people that have been hired are all Hillary Clinton supporters, some of them worked for Hillary Clinton. ... I mean, the whole thing is ridiculous if you want to know the truth.”

The Associated Press contributed to this report.