She said: "If the election had been on October 27th, I'd be your president"
Hillary Clinton has said she takes "absolute personal responsibility" for her election loss - but also blamed FBI Director James Comey and the leaking of emails connected to her campaign.
Mr Comey sent a letter to Congress less than two weeks before election day, indicating that his organisation was investigating newly discovered emails connected to Mrs Clinton's use of a private server while serving as US secretary of state.
Only days before the election, he announced no evidence of wrongdoing had been found.
US officials, meanwhile, are continuing to examine the alleged Russian influence in the campaign. Thousands of emails from the account of Mrs Clinton's campaign chairman John Podesta were released by WikiLeaks in the weeks leading up to the vote, with US intelligence agencies blaming Russia for the initial hack.
Mrs Clinton spoke extensively about the campaign during in an interview with CNN's Christiane Amanpour at a 'Women for Women International' event in New York.
"It wasn't a perfect campaign - there is no such thing," she argued. "I was on the way to winning until a combination of Jim Comey's letter on October 28th, and Russian Wikileaks raised doubts in the minds of people who were inclined to vote for me but got scared off.
"We overcame a lot in the campaign. We overcame an enormous barrage of negativity, of false equivalency and so much else. But as [independent pollster] Nate Silver [...] has concluded, if the election had been on October 27th, I'd be your president. And it wasn't."
She added: "Did we make mistakes? Of course we did. Did I make mistakes? Oh my gosh yes, you'll read my confession and my request for absolution. But the reason why I believe we lost were the intervening event in the last ten days."
She also spoke about the suspected Russian intervention during the election campaign, observing: "Every day that goes by, we find out more about the unprecedented inference, including from a foreign power whose leader is not a member of my fan club."
Mrs Clinton is writing a book about last year's campaign, and indicated it was a 'painful process' reliving her unsuccessful White House bid.
She also took a few opportunities to remark on Donald Trump, including the claim that he should worry less on the election and her "winning the popular vote".
"I did win more than three million than my opponent," she noted to applause from the crowd.
Mrs Clinton also said: "I'm back to being an activist citizen - and part of the resistance."