Senior Justice Department officials pushed back on the ABC News report, saying Rosenstein has not at this point requested any official opinion on the matter from career ethics attorneys in the department.
Mr Trump did not identify who "the man" was but appeared to be questioning the integrity of Deputy Attorney-General Rod Rosenstein - the Justice Department's number two official who appointed Mr Mueller on May 17 and wrote a memo to Mr Trump that was critical of Mr Comey's performance after the former director was sacked. Thursday night, Rosenstein issued an unusual statement complaining about leaks in the case.
While accusing the Clinton campaign and the Obama administration of indulging in illegal acts, Trump had said that "there was never a special counsel appointed to oversee the acts of his Democrat predecessors". "Witch Hunt", Trump tweeted on Friday morning. "That's undemocratic on its face and a blatant violation of the president's oath of office".
Aides have counseled the president to stay off Twitter and focus on other aspects of his job. They have tried to highlight the positive reviews he received Wednesday when he made a statesman-like appearance in the White House to address the nation after Rep. Steve Scalise was shot during a congressional baseball practice.
A source close to Trump's legal team insisted to the Guardian that "the president was not confirming the investigation". Still, the snowballing investigation has deeply angered Trump, who denies he has any nefarious ties to Russian Federation.
Friday's tweets are the latest in a week of angry social media responses by the president over a report by The Washington Post that Mueller was looking into whether Trump obstructed justice.
"Americans should be skeptical about anonymous allegations", Rosenstein said.
"It's basically all he talks about on the phone", said one adviser.
Nevada governor signs bill to revive solar industry
Senate Bill 554 was among the few nail-biter proposals that passed in the final hour of the 2017 legislative session on June 5. Bill Sandoval this week signed a bill that reinstates net metering for photovoltaic solar power systems.
"As a result, the Federal Bureau of Investigation is unlikely to regain public and congressional trust until it has a Director who understands the gravity of the mistakes", he wrote.
But Republicans also worry that Mr. Trump is giving Mueller more material to investigate all the time.
"President Trump has started the clock on the Rosenstein firing watch", said Evan Siegfried, a GOP strategist.
ABC News reported on Friday that Rosenstein has privately said he may need to recuse himself from matters relating to the Russian Federation probe, given that he could become a potential witness in the investigation.
Reports have alleged that Trump asked both men to publicly quash the credibility of the Russian Federation investigation. That left Rosenstein in charge of the Russian Federation probe.
Several news reports said Mueller plans to interview key US national security officials about Trump's comments seeking an end to the investigation of contacts his first national security adviser, Michael Flynn, had with Russia's ambassador to Washington, Sergey Kislyak.
The Twitter attacks came as Vice President Mike Pence hired a personal lawyer to represent him in the intensifying investigation.
Pence had taken over the transition team from New Jersey Governor Chris Christie. He has already been subpoenaed by the House intelligence committee.