The 2016 Democratic presidential nominee said in a podcast interview that aired Friday that Sanders didn't try to unify the party after losing the primary to her four years ago and that he and his supporters contributed to her loss to Donald Trump in the general election.

Asked by Emily Tisch Sussman of the podcast "Your Primary Playlist" what Sanders could do this time to unite the party against Trump, Clinton replied, "Well, he can do it, for one."

"That's not our experience from 2016," Clinton said.

Clinton's comments come just before Monday's first-in-the-nation caucuses in Iowa, where Sanders is bunched at the top of the polls with former Vice President Joe Biden, Massachusetts Sen. Elizabeth Warren and former South Bend, Indiana, Mayor Pete Buttigieg. The remarks are yet another reminder of the lasting scars of the the brutal 2016 primary battle between Sanders, whose supporters believe the contest was rigged in Clinton's favor, and Clinton, who has begrudged Sanders for not supporting her candidacy quickly enough after she clinched the nomination.

Sanders was unable to campaign in Iowa on Friday because of the impeachment trial of President Donald Trump in the Senate. But at an evening rally in Clive, Iowa, one of his highest profile supporters, Michigan Rep. Rashida Tlaib, led the crowd in booing Clinton.

At the first mention of Clinton's name, some in the crowd began booing, prompting the moderator to say, "We're not going to boo. We're classy" But Tlaib interjected: "No. I'll boo. Booooo!" That drew laughter and louder boos from the audience.

"You all know, I can't be quiet," Tlaib continued, laughing. "We're going to boo. It's alright. The haters will shut up on Monday, when we win."

The latest back and forth comes after last week, when Clinton raised doubts about whether she would endorse Sanders if he wins the 2020 Democratic nomination to face Trump. Clinton told The Hollywood Reporter in an interview that she's "not going to go there yet," but later took to Twitter to say her priority was to defeat Trump, "and, as I always have, I will do whatever I can to support our nominee."

The Sanders campaign didn't immediately respond Friday to requests for a reaction about Clinton's comments. Last week, Sanders refused to comment on Clinton's critical remarks, saying only in a statement, "Together, we are going to go forward and defeat the most dangerous president in American history."

In Friday's podcast, Clinton contrasted the conversations she had with Barack Obama in 2008 about unifying the party after he became the nominee with the conversations she had with Sanders in 2016 after it became clear she would come out on top. They were "like night and day," she said.

Although there was "no question" about her nomination, she said, Sanders' "campaign and his principal supporters were just very difficult and really constantly not just attacking me but my supporters."

At the Democratic National Convention, she said, Sanders' supporters were "booing Michelle Obama, John Lewis. It was very distressing and such a contrast between what we did to unite in '08."

"All the way up until the end, a lot of people highly identified with (Sanders') campaign, were urging people to vote third party, urging people not to vote — it had an impact," she said.

Clinton, who narrowly defeated Sanders in Iowa in 2016 but lost the state to Obama in 2008, also criticized the caucus process as "an undemocratic way of picking the nominee."

"I'll be happy to see the primaries start rolling around because that's a much easier way for people to participate and for the outcomes to be much clearer," she said.