US Vice President Joe Biden has praised Vermont Senator and Democratic presidential candidate Bernie Sanders for "thinking big" when it comes to how to lead the country.

"I like the idea of saying, 'We can do much more,' because we can," Biden told The New York Times in an interview published Thursday.

Sanders' critics, most notably his chief rival Hillary Clinton and her surrogates, often question how realistic his proposals are, but Biden dismissed that concern.

"I don't think any Democrat's ever won saying, 'We can't think that big — we ought to really downsize here because it's not realistic,'" Biden said. "C'mon man, this is the Democratic Party! I'm not part of the party that says, 'Well, we can't do it.'"

The vice president, who considered entering the White House race himself, praised Sanders for aiming high even if it doesn't work out.

"Presidents have always been told by really smart people: 'Don't push something that you can't succeed in — it diminishes your power,'" he said. "I completely disagree with that proposition."

"Everything I've ever cared about, with the exception of the President's brilliant passage of the Affordable Care Act, takes time," he added. "The only way to get these big things done is talk about them."

It's not the first time Biden has made comments interpreted as boosting Sanders. During a CNN interview in January, Biden praised Sanders' fight on income inequality and said Clinton was "relatively new" to the effort.

Sanders has repeatedly condemned America’s huge wealth inequality, lack of universal healthcare and a corrupt campaign finance system, drawing significant support for his presidential campaign.

Biden, who has wanted the top spot for decades, said he regrets "every day" that he didn't enter the 2016 presidential race -- but that his decision was in his family's best interests.

"I regret it every day, but it was the right decision for my family and for me. And I plan on staying deeply involved," Biden said in January.