Sen. Elizabeth Warren Elizabeth WarrenWarren, Schumer introduce plan for next president to cancel ,000 in student debt The Hill's 12:30 Report - Presented by Facebook - Don't expect a government check anytime soon No new taxes for the ultra rich — fix bad tax policy instead MORE (D-Mass.) and former South Bend, Ind., Mayor Pete Buttigieg Pete ButtigiegBogeymen of the far left deserve a place in any Biden administration Overnight Defense: Woodward book causes new firestorm | Book says Trump lashed out at generals, told Woodward about secret weapons system | US withdrawing thousands of troops from Iraq A socially and environmentally just way to fight climate change MORE tangled over the costs associated with their health care proposals at Tuesday's Democratic debate.

Warren, who supports "Medicare for All," said Buttigieg's plan to create a public option costs less because it's only a "small improvement" over the current system.

"They're improvements over where we are now but they are small improvements," Warren said. "That's why they cost so much less."

Medicare for All would cover every American and replace private insurers, at a cost of about $30 trillion over 10 years, according to some estimates.

Buttigieg's campaign has said his plan, which would create a public option to compete with private insurance, would cost $1.5 trillion over a decade.

"We've got to move past the Washington mentality that suggests that the bigness of plans only consists of how many trillions of dollars they put through the Treasury," Buttigieg said Tuesday.

Warren has talked less about Medicare for All on the campaign trail amid declining poll numbers.

While she defended the cost of her health plan during Tuesday's debate, she shifted the conversation toward defending and building on the 2010 Affordable Care Act and lowering the costs of prescription drugs.

"I have a plan to expand health care. But let's keep in mind when it comes to the general election, we Democrats are up against a Republican incumbent who has cut health care. I'll take our side of the argument any day," she said.