After former Vice President Joe Biden attacked Medicare for All, decriminalization of border crossings, and other major progressive agenda items during an interview that aired Friday morning, fellow 2020 White House contender Bernie Sanders responded that bold ideas will be necessary to "energize voters" and defeat President Donald Trump.

"I'm proud to be working with AOC and so many other Democrats to pass Medicare for All, debt-free college, and a Green New Deal," Sanders tweeted, referring to Rep. Alexandria Ocasio-Cortez (D-N.Y.). "This is the agenda America needs."

I’m proud to be working with @AOC and so many other Democrats to pass Medicare for All, debt free college and a Green New Deal. This is the agenda America needs — and that will energize voters to defeat Donald Trump. https://t.co/MPS9fDsuCH — Bernie Sanders (@BernieSanders) July 5, 2019

Biden was asked by CNN's Chris Cuomo whether he supports "big" ideas like tuition-free public college and student debt cancellation—two policies backed by Sanders.

"For example, I think there should be healthcare for everyone. I have a plan how to do that that's rational, and will cost a hell of a lot less, and will work," said Biden, who has not put out a healthcare plan.

Biden suggested he supports allowing Americans to buy in to Medicare instead of going all the way to Medicare for All, which he slammed as disruptive and costly despite studies showing it would save the U.S. trillions of dollars in overall healthcare spending.

"If they like their employer-based insurance, which a lot of unions broke their neck to get, a lot of people like theirs, they shouldn't have to give it up," Biden said. "If you don't go my way and you go their way you have to give up all that. What's gonna happen when you have 300 million people landing on a healthcare plan. How long is that going to take? What's it going to do?"

Biden: "If you provide an option for anybody who in fact wants to buy into Medicare for All, they can buy in. They buy in and they can do it. But if they like their employer-based insurance, which a lot of unions broke their neck to get... they shouldn't have to give it up" pic.twitter.com/iQXEw2M01F — CNN Politics (@CNNPolitics) July 5, 2019

On the topic of immigration, Biden said he doesn't agree with calls to decriminalize entering the U.S. without documentation, a proposal put forth by Julián Castro and backed by Sen. Elizabeth Warren (D-Mass.).

"No, I don't," Biden said when asked if he supports the proposal. "I think people should have to get in line, but if people are coming because they're actually seeking asylum, they should have a chance to make their case."

The former vice president also downplayed Ocasio-Cortez's victory over Rep. Joe Crowley last year and suggested her ideas don't have broad appeal.

"I think Ocasio-Cortez is a brilliant, bright woman, but she won a primary," Biden said. "In the general election fights, who won? Mainstream Democrats who are very progressive on social issues and very strong on education and healthcare."

Biden: “I think Ocasio-Cortez is a brilliant, bright woman, but she won a primary. In the general election fights, who won? Mainstream Democrats who are very progressive on social issues, and very strong on education, health care.” https://t.co/F8L4wlRkWN pic.twitter.com/sTO5RXCj34 — CNN (@CNN) July 5, 2019

Biden's comments on Ocasio-Cortez sparked immediate backlash:

1) AOC won a general election also. Biden hasn't successfully won a presidential primary despite multiple attempts 2) We see AOC leading charge against racist CBP, we see Biden defending segregation 3) Progressives almost won GA & FL. GOP vote suppression was major factor https://t.co/Yq67PLuEJm — Bree Newsome Bass (@BreeNewsome) July 5, 2019

"As I've said many times," tweeted Intercept columnist Shaun King, "every time Joe Biden opens his mouth he gets himself in trouble. It's why this is the first interview he's done in months."