"Oh, I've talked to Bernie, Bernie's going to endorse her, this is going to work out," Biden told National Public Radio in an interview for "Weekend Edition" that will air on Sunday. A portion of the interview was released Thursday evening.
"The Democrats are coalescing even before this occurs," he added.
Sanders has yet to formally back Clinton, who clinched the nomination earlier this month. He's working to ensure his top agenda items -- including combating income inequality and reforming the banking system -- are taken up by Clinton and other Democrats this election year.
However, the Vermont senator did say last week he would likely vote for Clinton
in November, regarding her as the most probable candidate to beat Donald Trump, the presumptive GOP nominee.
Asked about Biden's remarks on MSNBC on Thursday, Sanders said he had last spoken with Biden three weeks ago. He didn't deny that he would endorse Clinton but also declined to confirm Biden's comments.
"I said, 'Right now, my hope is that we can reach an agreement on some very important issues and I can go forward to the millions of people who supported me and say, look, this is the progress you have made. This is where we're going to go as a country.' So I hope it happens. As of this moment, we're not there quite yet."
Other top party leaders, including Biden, President Barack Obama and Sen. Elizabeth Warren have all thrown their support behind Clinton. Biden's endorsement
was low-key, without the type of hyped rollout that accompanied Obama's public backing of Clinton.
But Biden has begun mentioning his support for Clinton regularly, saying he's ready to work to help her get elected.
Biden has also had effusive praise for Sanders, celebrating his longstanding focus on issues of inequality. Biden met Sanders earlier this month at the Naval Observatory following an Oval Office sitdown between Obama and the candidate.
Warren stumped for Clinton on Monday, and both Obama
will appear on the campaign trail for her next week.
Obama will campaign for Clinton in Charlotte, a return to the city where he was formally nominated as the Democratic nominee in 2012. The event is scheduled to take place at the same venue.
Meanwhile, Biden pitches Clinton in Scranton, his hometown.
"Those folks back home know me. And they know my shortcomings, and I have a lot of them, and they know my strengths," Biden told NPR, arguing that familiarity will help him vouch for Clinton.
"I understand the hardest thing to do is not writing the check. The hardest thing is vouching. When you vouch for them you say 'I'm putting my reputation on the line, I believe this person is a good person, has character," Biden said. "You're putting your rep on the line you're saying I think this person has character and that's what I'm prepared to do for Hillary."