Bernie Sanders unveiled his plan for 'universal childcare' in an interview Sunday – saying the new federal benefit will be funded by a tax on wealth.

The senator from Vermont defended the plan even as he takes fire from more centrist presidential rivals who have questioned the multi-trillion cost of his Medicare for All plan.

'It's taxes on billionaires,' he told host Anderson Cooper on CBS' '60 Minutes' Sunday.

Vermont Sen. Bernie Sanders defended his plan for 'universal childcare' on '60 Minutes' Sunday

'You know, I get a little bit tired of hearing my opponents saying-- 'Gee, how you going to pay for a program that impacts and helps children or working class families or middle class families? How you going to pay for that?'' Sanders said.

'And yet, where are people saying, 'How are you going to pay for over $750 billion on military spending?' How you going to pay for a trillion dollars in tax breaks to the 1% in large corporations which was what Trump did?' he said.

'How you going to pay for a trillion dollars in tax breaks to the 1 per cent in large corporations which was what [President] Trump did? When you help the billionaires and you help Wall Street, 'Hey!' Of course we can pay for it. That's what America's supposed to be about.' Well, I disagree,' he said.

Principal Kevin Bowles and vice principal Sophia Tkac introduce their comfort dogs Brightly (r.) and Shine to a pre-kindergarten class at New Bridges Elementary school, on October 30, 2017 in Brooklyn, New York, New York

Sanders called it 'shocking' that he is now the Democratic frontrunner

Democratic presidential candidate Sen. Bernie Sanders, I-Vt., waves to his supporters during a campaign event on Sunday, Feb. 23, 2020, in Austin, Texas

Sanders' plan would provide coverage for Americans with children up to age four, which would include child care and pre-K schooling. Sanders' camp puts the cost at $1.5 trillion.

By taxing the extreme wealth of the top 0.1 percent, we can invest $1.5 trillion over the next decade on guaranteeing free, universal, quality child care and early education for all,' it says in the ninth paragraph of its description of the plan.

When Cooper pressed Sanders on how much the plan would cost, he was vague, but agreed he didn't have a price tag for all his plans.

'No, I don't. We try to – you mentioned making public colleges and universities tuition free and cancelling all student debt, that's correct. That's what I want to do. We pay for that through a modest tax on Wall Street speculation,' he said.

'But you say you don't know what the total price is, but you know how it's going to be paid for. How do you know it's going to be paid for if you don't know how much the price is?' Cooper pressed.

'Well, I can't – you know, I can't rattle off to you ever nickel and every dime. But we have accounted for – you talked about Medicare for All. We have options out there that will pay for it,' Sanders responded.

'Childcare must be guaranteed for every child regardless of their parents' income, just like K-12 education,' he said in a statement. 'We know that the first four years of a child's life are the most important years of human development, so it is unconscionable that in the wealthiest country in the world, we do not properly invest in early childhood education.'

The government would set minimum wages for child care workers and guarantee ''low child-to-adult ratios and small group sizes' in the classes. The programs would be administered by states and local governments but funded by the feds – a federal model that only hints at what might happen if some states opt out, as they did even when provided near 100 per cent federal reimbursement for increased Medicaid programs under Obamacare.

Sanders trounced rivals in Nevada, and is competing for supremacy with former Vice President Joe Biden in South Carolina, which votes Saturday.

Former South Bend mayor Pete Buttigieg blasted the self-described democratic socialist candidate for believing 'capitalism is the root of all evil' during a speech in Las Vegas Saturday.

'Senator Sanders believes in an inflexible, ideological revolution that leaves out most Democrats, not to mention most Americans,' Buttigieg said.

Sanders in the interview acknowledged he was now the frontrunner in the fight for the Democratic nomination, a development he called ''a bit shocking.' He agreed with Cooper that the Democratic Party has moved towards him.

'And the ideas that seemed radical four years ago are now kind of mainstream,' he said.