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. Comey also testified he had told Trump he was not under investigation.
Trump, who celebrated his 71st birthday Wednesday, refrained from commenting until Thursday morning.
In a second Tweet, Trump echoed previous claims that he is the victim of what he says is the "single greatest witch hunt in American political history".
President Donald Trump has taken on "obsessive behavior", constantly sending out defensive tweets, saving morning news programs to watch later and even blurting out during meetings that he's not under investigation, Politico reported Thursday.More news: Cladding used in London's Grenfell Tower is 'banned in Britain'
Sessions explained to the Senate Intelligence Committee that Comey's concern pertained to the protocol though which the Department of Justice communicated with the White House.
There has been no indication that Mr Mueller told the president to fire Mr Comey.
The new allegations against Trump center on his own admission that he fired Comey because of the Russian Federation investigation, and suggestions he asked several top intelligence officials for their help altering the inquiry's direction.
In a tweet, the president also seemed to accuse the USA deputy attorney general of pursuing a "Witch Hunt".More news: Twelve Top US Universities Reaffirm Commitment to Climate Change Pact
Trump appeared to be responding to reports this week that the FBI is investigating Trump's decision to fire FBI Director James Comey and his apparent attempts to quash the bureau's investigation of former National Security Adviser Michael Flynn.
Director of National Intelligence Daniel Coats, National Security Agency's head Mike Rogers, and Rogers's recently departed deputy Richard Ledgett agreed to be interviewed by Mueller's investigators as early as this week, the Post reported.More news: Protests Following Afghan Blasts Call for Security Chiefs to Step Down
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