Hillary Clinton said that attempts by the Kremlin to influence the U.S. presidential election are designed to help Donald Trump, whom she accused of being close to Russian strongman Vladimir Putin.

"We have never in the history of our country been in a situation where an adversary, a foreign power is working so hard to influence the outcome of the election and believe me, they're not doing it to get me elected," she said. "They're doing it to try to influence the election for Donald Trump."

On Friday, the U.S. formally blamed Russia for recent political hacking attacks, saying they were "intended to interfere with the U.S. election process." U.S. intelligence officials said they are "confident" that the Russian government directed those attacks on American political organizations, the Department of Homeland Security and the Office of the Director of National Intelligence on Election Security said Friday in a joint statement.

Clinton said that while it isn't clear why the Russians would be interested in helping the New York businessman, she said Trump should release his tax returns so that the American people can see if there is a conflict of interest.

Trump responded by calling her comments "ridiculous" and that she's been "caught in a total lie."