(CNN) Former Director of National Intelligence James Clapper said Friday night that the intelligence community's assessment of Russian interference in the 2016 presidential race "cast doubt" on the legitimacy of President Donald Trump's victory.

"Our intelligence community assessment did, I think, serve to cast doubt on the legitimacy of his victory in the election," Clapper said on CNN's "Erin Burnett Out Front."

Clapper said he disclosed the information to the President during a briefing on the assessment in January, and that particular aspect seemed to concern Trump the most.

"I think that transcends, unfortunately, the real concern here, which is Russian interference in our political process, which by the way is going to continue," Clapper said.

The revelation came hours after the President tweeted about the "Russian hoax," writing "the greatest influence over our election was the Fake News Media 'screaming' for Crooked Hillary Clinton." At a rally in Alabama later Friday evening, Trump doubled down, saying, "No, Russia did not help me, that I can tell you, OK?"

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