Des Moines, Iowa (CNN) Former Vice President Joe Biden said in an exclusive interview with CNN airing Friday that he wasn't prepared for California Sen. Kamala Harris to confront him on issues of race the way she did at the first Democratic primary debate .

Biden told CNN's Chris Cuomo that while he was prepared to be a focal point at last week's debate, he didn't anticipate that Harris would be the candidate leading the charge. He also said he didn't expect to be faulted on issues of race, given his record on civil rights.

"I was prepared for them to come after me, but I wasn't prepared for the person coming at me the way she came at me," Biden told Cuomo on Thursday evening in Iowa, adding that he felt that way in part because he knew Harris well and Harris knew his late son, Beau Biden, too.

Harris, a former prosecutor , confronted Biden over his decades-old Senate fight against busing to desegregate schools and comments about his ability to be civil and work with segregationist senators. The clash defined the second night of the debate and has helped boost Harris in post-debate polls, bringing Biden's once-high numbers closer to the pack of Democratic presidential hopefuls.

In the interview, Biden also expressed deep skepticism of the leftward tilt of the Democratic Party, suggesting that " Medicare for All " is irrational, arguing that the majority of Democrats are "center left" not "way left," and saying Rep. Alexandria Ocasio-Cortez , while "brilliant" and "bright," does not represent Democrats who can win a general election in a competitive district or state.

Biden on Trump: "He's the bully that I knew my whole life"

But Biden , keenly aware the polls show Democrats care deeply about candidates' ability to beat President Donald Trump in 2020, spent considerable time in the interview looking toward that goal. He told Cuomo that he was familiar with the President because he was like "the bully that I've always stood up to."

"The idea that I'd be intimidated by Donald Trump," Biden said with a look that suggested that notion would be foolish. "He's the bully that I knew my whole life. He's the bully that I've always stood up to. He's the bully that used to make fun when I was a kid that I stutter, and I'd smack him in the mouth."

Biden, leaning forward as he spoke, repeated that he is unafraid of Trump and appeared to reference the moment in a debate between Trump and Democratic nominee Hillary Clinton when the then-presidential candidate stood behind the former secretary of state as she spoke, crowding her on national television.

"I'm looking forward to this man. You walk behind me in the debate. Come here, man," Biden said, flicking his hands toward himself.

Biden faulted Trump on policy throughout the interview, including his handling of China -- "while he's tweeting, China's going to own the 5G market"-- and North Korea.

"Look, you want to talk, you want to deal with us, you want sanctions lifted. Show me something ahead of time," Biden said of North Korea, faulting Trump for his openness with the rogue nation and its leader, Kim Jong Un.

Biden says his busing position was taken "out of context"

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Before taking on Trump, however, Biden will need to get through the crowded field of Democrats who are also vying for a chance to challenge the Republican President.

And over the last week, it has been the confrontation between Biden and Harris that has defined the race.

Harris' campaign communications director, Lily Adams, told CNN that she didn't view the moment as a personal attack against Biden.

"I can't speak to why he was or wasn't prepared. That's for him and his team to decide and to explain. But what she was pointing out was a very real disagreement on the record," Adams said on "New Day" Friday.

Biden said that his decades-old position against federally mandated busing to desegregate schools was "taken out of context" by Harris during the debate.

Biden added that he is frustrated the debate was so focused on decades-old policy, not what each candidate wants to do going forward. The former vice president said he will hold off going after his opponents' previous positions because he doesn't want the debate between Democrats to be backward looking.

"I get all this information about other people's past and what they've done and not done. And, you know, I am just not going to go there," Biden said. "If we keep doing that, that's, I mean, we should be debating what we do from here."

But that didn't stop him from attempting to quell the continued focus on the debate moment. He told CNN that "our positions aren't any different, as we're finding out."

Since the debate moment, Harris and her campaign have struggled to explain her own position on busing to desegregate schools today. And animosity between the two campaigns has spilled out into the open, with top aides to Biden and Harris engaging in a heated back-and-forth on social media over where their respective candidates stand on the issue.

Biden stood by his past positions on busing, telling Cuomo that "busing did not work."

"You had overwhelming response from the African American community in my state," Biden said of Delaware. "They were, they did not support it. They did not support it."

But the former vice president argued that the entire debate between Harris and him over busing centered on "how do you equalize education in every area." On that measure, he said, he has the best plans, noting that he wants to triple funding for the most disadvantaged schools and have preschool available from age 3.

"Every child out there is capable, but they're living in circumstances that make it difficult," Biden said. "So what are we doing? We're sitting around here as if it's an insoluble problem."

Biden, though, never made that argument during the debate, largely ceding the point to Harris during the nationally televised moment.

Asked on Thursday why he didn't push back as forcefully as he is now, Biden said, "What I didn't want to do is get in that scrum. Do you think the American public looked at that debate, take me out of it, and thought, boy, I really liked the way that's being conducted?"