In a series of statements on Twitter on Thursday, Mr Trump repeated his claim that Mr Mueller's investigation is a "WITCH HUNT" based on the "phony" premise of possible collusion between Russian Federation and a cadre of Trump campaign associates.
A spokesman for government lawyers declined to comment.
Rod Rosenstein, the deputy attorney general, appointed former FBI Director Robert Mueller as a special prosecutor in an investigation of alleged collusion between Trump associates and Russian Federation in the 2016 election. "Witch Hunt", Trump wrote on Twitter.
"Well, we were asked our opinion, and when we expressed it, which was consistent with the memorandum and the letter we wrote, I felt comfortable. and I guess the deputy attorney general did too", he said, "in providing that information in writing".
Trump and his supporters cast Comey's testimony that he had told the president he was not personally under investigation as vindication. Why would the president object to a thorough investigation - unless he had something to hide?
Trump on Friday said the person conducting that probe was the individual who had told him to dismiss James Comey, who had been at the head of the bureau from 2013 until he was sacked early last month.
"Sad!" the president tweeted Friday. "That's undemocratic on its face and a blatant violation of the president's oath of office", said Feinstein. The responsibility would fall to Congress to review any findings of misconduct.
Yet Trump's angry tweets on Friday underscored the near-impossible challenge his advisers and legal team have in trying to get him to avoid weighing in on an active probe.
Meanwhile, the top attorney for the Trump transition team has ordered the organization's staff to preserve all records related to Mueller's widening investigation.
The tweets came shortly after Rosenstein issued his unusual statement that appeared to be warning about the accuracy of such reports. Americans should be skeptical about anonymous allegations.
Raw Story's Sarah K. Burris said, "The statement left the internet wondering if it was forced by President Donald Trump - or if the Justice Department was hacked".
"I'm not going to answer hypothetical questions", Rosenstein said.
The transition official spoke on condition of anonymity because the person was not authorized to discuss post-election decisions publicly.
In his tweet, Trump says he was "told" to fire Comey, but the commander in chief normally doesn't take orders from members of his administration.
Mueller's investigative team has expanded in recent weeks.
He had written a memorandum to US Attorney General Jeff Sessions, criticising Mr Comey about the way in which he handled the Russian Federation investigation.
Rosenstein told Brand that she would take over those responsibilities once he removes himself from the investigation. He testified that he leaked information about the notes through a friend to the Times to increase pressure for the appointment of a special prosecutor after he concluded Trump's administration "defamed" him and the Federal Bureau of Investigation after his May 9 firing.
Even yesterday, Trump had termed the alleged links between Russian Federation and his campaign as a phony story. They are: Flynn; Paul Manafort, Trump's former campaign manager; Rick Gates, Manafort's business partner; Carter Page, a former foreign policy adviser; and Roger J. Stone Jr., an informal adviser to Mr. Trump.
"He brought that recommendation to the President" and Trump agreed, Pence concluded. The latest reports suggest that Trump considered the possibility, though his aides managed to talk him out of it.
Be Civil - It's OK to have a difference in opinion but there's no need to be a jerk.