Former CIA Director John Brennan John Owen BrennanJournalism or partisanship? The media's mistakes of 2016 continue in 2020 Comey on Clinton tweet: 'I regret only being involved in the 2016 election' Ex-CIA Director Brennan questioned for 8 hours in Durham review of Russia probe MORE on Wednesday said that "at least one voter" was swayed by Russia's campaign to interfere in the 2016 presidential election.

Brennan, who headed the CIA under former President Obama from 2013 to 2017, said at the National Press Club in Washington, D.C., that he was “sure, personally, that those Russian efforts changed the mind of at least one voter," according to Reuters.

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“Whether it was one voter or a million voters, I don’t know,” Brennan added, before later acknowledging that the view was his own and did not reflect on the intelligence agency. The CIA did not assess how Russia's coordinated effort to interfere in the election impacted the feelings of voters.

“How many, in which states, I don’t know. Whether it changed the outcome, I don’t know,” Brennan said.

Brennan has been a fierce critic of President Trump Donald John TrumpFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Former Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick MORE amid his two-plus years in the White House. The former CIA director has repeatedly criticized the president's conduct and has said that Trump's claims that no one on his campaign colluded with Russia are "hogwash."

Trump last year revoked Brennan's security clearance because of what the White House called his “unfounded and outrageous allegations."

Lawmakers and intelligence agencies have concluded that Russia launched a coordinated effort involving hacks, leaks and social media campaigns to interfere in the U.S. elections in 2016. U.S. officials have been careful about expressing with certainty that Russia's efforts persuaded voters, Reuters noted.

The Senate Intelligence Committee released a report in July concluding that Russia targeted election systems in all 50 states in 2016. The report noted that there is no evidence that the campaign changed any votes in actual voting machines.

The panel in early October urged Congress to take further action on election security to prevent Russian disinformation efforts from affecting the 2020 election.