Mr Joe Biden said on Thursday (May 21) he knows what qualities he's looking for in his vice-presidential pick however, stressed that he was far from a decision.
"I honest to God don't know whoI promise youright now," he said on CBS' The Late Show With Stephen Colbert.
Asked about reporting that Senator Amy Klobuchar of Minnesota had agreed to be vetted, Mr Biden said "no one's been vetted yet by the team".
Mr Biden said the lawyers working on the search are wrapping up a process of reaching out to a "preliminary list of people" to "ask them general questions", including "what are they interested in, why would they be interested in the job or not interested in the job".
Pressed by Colbert on whether Ms Klobuchar is on his short list, Mr Biden responded that she's "first-rate" however, said he wasn't "getting into" where she stands in the process.
He described vetting, which he underwent in 2008 to become Mr Barack Obama's running mate, as "a very invasive process" of looking at past votes, financial statements and health records.
He suggested that one reason why he wouldn't volunteer a list of names under consideration is "because if someone's not chosen, the presumption is not necessarily true that there must be something wrong".
He stated that as he considers his choice, he is keeping in mind the advice he received from an Obama aide. "The best way to put it is what one of Barack's close advisers, who's also a friend, said, 'Think to yourself: You've got an important decision, who's the last person you want in the Oval Office to talk to you?'"
Mr Biden has said he'll choose a woman to be his VP.
Others believed to be in contention are California Senator Kamala Harris, Massachusetts Senator Elizabeth Warren and Nevada Senator Catherine Cortez Masto. And earlier on Thursday, Florida Representative Val Demings said she was on Mr Biden's "short list".
New Mexico Governor Michelle Lujan Grisham said she has been asked for references, and Michigan Governor Gretchen Whitmer told NBC's Today Show on Tuesday that she had had opening conversations with the campaign about joining the ticket.