Washington (CNN) The top Democrat on the Senate Intelligence Committee rebutted President Donald Trump on Sunday, questioning his response to former national security adviser Michael Flynn's guilty plea and backing former FBI Director James Comey.

"The President is somehow saying he fired Flynn because he knew Flynn was lying to (Vice President Mike) Pence," Virginia Democratic Sen. Mark Warner said. "Well if he knew that then, why didn't he act on it earlier?"

Warner, speaking Sunday on CNN's "State of the Union," was responding to Trump's tweet Saturday on Flynn's guilty plea, in which he suggested he was aware Flynn had lied to the FBI when he fired the former general.

"I had to fire General Flynn because he lied to the Vice President and the FBI," Trump tweeted. "He has pled guilty to those lies. It is a shame because his actions during the transition were lawful. There was nothing to hide!"

I had to fire General Flynn because he lied to the Vice President and the FBI. He has pled guilty to those lies. It is a shame because his actions during the transition were lawful. There was nothing to hide! — Donald J. Trump (@realDonaldTrump) December 2, 2017

Warner anticipated that because Flynn was only charged with one crime, it was more likely that Flynn had more information to provide than what has already been made public.

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