Former US vice president Joe Biden says he believed he never acted inappropriately in the face of allegations by a female activist that he kissed her at a campaign event in 2014.

“In my many years on the campaign trail and in public life, I have offered countless handshakes, hugs, expressions of affection, support and comfort,” Mr Biden said in a statement Monday morning (Australian time).

“And not once – never – did I believe I acted inappropriately. If it is suggested I did so, I will listen respectfully. But it was never my intention,” he added.

Mr Biden, has not yet said whether he will run for president in 2020 but is expected to announce his intention soon, has said he does not recall the 2014 incident.

The allegation was made in an online essay published on Friday by Lucy Flores, a party activist who was running to be Nevada’s lieutenant governor.

Ms Flores said Mr Biden also touched her shoulders and smelled her hair when they appeared at an event together, making her feel uncomfortable.

In his statement Mr Biden added: “I may not recall these moments the same way, and I may be surprised at what I hear.

“But we have arrived at an important time when women feel they can and should relate their experiences, and men should pay attention. And I will.”

Speaking on Sunday to CNN, Ms Flores said she was glad that Mr Biden was willing to listen, but demanded that he acknowledge that his behaviour was wrong.

“If he’s saying that he never believed that was inappropriate then, frankly, I think that’s a little bit of a disconnect,” she said.

“I want him to change his behaviour. I want him to acknowledge that it was wrong.”

Mr Biden served eight years as vice president under former president Barack Obama and 36 years in the US Senate.

-with AAP