Trump is being investigated for alleged obstruction of justice, according to officials who spoke to the Washington Post What is Mueller investigating?
The newspaper reported on Wednesday that director of national intelligence Dan Coats, head of the National Security Agency Mike Rogers, and former deputy director at the NSA Richard Ledgett, had agreed to be interviewed by Mr Mueller's investigators as early as this week.
According to a report by the Washington Post on 15 May 2017, Mueller is also following up on allegations that Trump tried to obstruct the course of justice in his dealings with Comey.
"The FBI leak of information regarding the President is outrageous, inexcusable and illegal", Corallo told CNN.
Trump's attorney, Marc Kasowitz, did not respond to a BuzzFeed News request for comment, but did not deny the Post report in a statement issued to media after the story was published.
At Vox, Ezra Klein details how the latest developments in the case exemplify how Trump continues to create his own legal troubles.
Last week, in addition to saying he was sacked over the Russian Federation investigation, Comey accused the White House of spreading "lies, plain and simple" about him and the FBI. "Nice", he tweeted Thursday morning.
A cornered White House could try and use executive privilege to try to block officials from speaking to Mueller's team, although the US Supreme Court ruled during the Watergate scandal that officials cannot use privilege to withhold evidence in criminal prosecutions.
After Comey's testimony, Trump said he had been vindicated because the former FBI director confirmed telling Trump on three occasions that he was not under investigation.
Mueller was appointed after Trump dismissed Comey, who had been leading the inquiry.
Comey also testified that he had told Trump he was not under investigation.
A source familiar with the matter later told CNN that Mueller's investigators have asked for information and will talk to Coats and Rogers.
"Trump had received private assurances from then-FBI Director James B. Comey starting in January that he was not personally under investigation". Chuck Grassley of Iowa states that the committee "has an obligation to fully investigate any alleged improper partisan interference in law enforcement investigations".
"The way it was described to us, is a file has been opened on the president for the first time that is looking at him for obstruction - potentially for obstruction of justice".