Biden said it was never his intention to make women feel discomfort.
"In my many years on the campaign trail and in public life, I have offered countless handshakes, hugs, expressions of affection, support and comfort," he said. "And not once — never — did I believe I acted inappropriately. If it is suggested I did so, I will listen respectfully."
Flores' account of the 2014 incident comes at a crucial moment for Biden.
He's been wrestling for months with a final decision on whether to run for president, blowing through several self-imposed deadlines.
The Democratic primary has sped on without him, with more than a dozen candidates in the race, including a record number of women and minorities.
Veterans like Vermont Senator Bernie Sanders have shown surprising strength, while newer White House hopefuls like California Senator Kamala Harris and Texan Beto O'Rourke have drawn big crowds and displayed early fundraising prowess.
Biden still leads most early polls, buoyed by broad name recognition and the goodwill he generated during eight years as President Barack Obama's No. 2.
Given his experience and appeal with white working-class voters in Midwestern battleground states, he's also seen by some Democrats as the best-positioned candidate to defeat President Donald Trump.
Nancy Bobo, an Iowa activist who was among Obama's earliest supporters in the state, shares that view. She fears the episode with Flores suggests Democrats may try to tear down their most-qualified candidate.
"I can just see what's coming at him," Bobo said." And it's going to come at him from the Democrats."
None of Biden's potential rivals defended him following Flores' allegations. Massachusetts Senator Elizabeth Warren said she believed Flores and said Biden "needs to give an answer" about what occurred.
White House counsellor Kellyanne Conway said Flores was "quite bold" to "go up against the highest levels of her political party" with the allegations and suggested that Biden should consider apologising to Flores.
Conway deflected questions about the numerous women who have accused Trump of sexual misconduct, allegations he denies.
Flores told AP that she had been mulling coming forward for years. The tipping point for her, she said, was Biden's meeting in March with 2018 Georgia Democratic gubernatorial nominee Stacey Abrams.
"I saw that she was meeting with him and I thought to myself that if I don't say something now, I'm going to regret this."
Flores said she approached only New York Magazine to publish her account of her encounter with Biden and that the magazine had fact-checked the piece after she submitted it.
She said that she had provided New York with the names of several people she confided with about the incident soon after it occurred. She said she also "shared a conversation with a former staffer" about the episode.
Flores declined to name any of those people to AP, saying that "no one is willing to speak publicly."
AP tried to contact several advisers and aides from Flores' 2014 campaign, but was unable to obtain any independent verification of her account.
Flores said Biden's team has not been in touch with her since her story was published. She said she would be satisfied if Biden simply acknowledged the discomfort the episode caused her.
"I do think that if he truly wants to listen, he will make himself available," she said.
Biden has been warned by advisers that his past statements and actions, including his long history of hugging and showing affection to women, would face fresh scrutiny in the 2020 campaign.
In some cases, Biden's policy positions, such as his support for the 1994 crime bill that is blamed for mass incarcerations of minorities, are out of step with a party that has shifted to the left. But at other moments, like when he touts his ability to forge compromises with Republicans, he can appear to be speaking about a political era that many Democrats believe no longer exists.
Karen Finney, a Democratic strategist who worked on Hillary Clinton's 2016 campaign, said Biden's team needs to answer a key question before launching a White House bid: "Do they feel confident in their ability to understand this electorate and campaign in 2020, which is already different than 2016?"
Even before Flores made her allegations, some Democrats were wondering whether Biden was meant for his moment.
His team was widely panned following reports that they were considering tapping a younger Democrat or a minority like Abrams as a running mate early in the primary in an attempt to counteract questions about Biden's age.
While Biden's team denied that he was considering that step, Biden did float the idea to Abrams over a recent lunch, according to a Democrat with knowledge of the discussion.
Flores, a former Nevada state representative and the 2014 Democratic nominee for Nevada lieutenant governor, wrote that the incident with Biden occurred as the two were waiting to take the stage during a rally in Las Vegas.
"I felt two hands on my shoulders. I froze. 'Why is the Vice-President of the United States touching me?'" she wrote. "He proceeded to plant a big slow kiss on the back of my head."
Biden spokesman Bill Russo said the former Vice-President doesn't remember kissing Flores.
Democratic strategist Rebecca Katz said that while Flores' descriptions may feel familiar to those who have watched Biden hug and hold hands with women for years, she put the focus on the women who were on the receiving end of his affections.
"What Lucy Flores so bravely did is say, 'This is the way he made me feel,'" Katz said. "No one has ever done that before with Joe Biden."
- AP
