Sen. Bernie Sanders defended his Medicare for All plan on the campaign trail in Iowa, telling ABC News that it's "much more progressive in terms of protecting the financial well being of middle income families" than Sen. Elizabeth Warren's plan, which she unveiled last week.

Why it matters: Warren has frequently said she's "with Bernie" on Medicare for All, but the health care truce between two of the most progressive candidates in the race seemingly broke with Warren's newly released plan.

Details: The main difference between Sander's and Warren's plans is middle-class taxes. Sanders has said he is open to increasing taxes on middle-class Americans, but he has yet to release a detailed plan of how to finance his single-payer Medicare for All plan.

Warren claims that her plan would not take "one penny in middle-class tax increases."

Instead, Warren would pay for the plan — which would cost $20.5 trillion over 10 years — by taxing corporations and the richest 1% of Americans, reallocating defense spending and cracking down on tax fraud and evasion.

Her plan would also create a formula for employer contributions to Medicare for All based on their health care spending.

What they're saying: Sanders also told ABC News that he believes Warren's plan could harm job creation by drawing funds from employers.

“I think that that would probably have a very negative impact on creating those jobs, or providing wages, increased wages and benefits for those workers. ... So I think we have a better way, which is a 7.5% payroll tax, which is far more I think progressive, because it’ll not impact employers of low wage workers but hit significantly employers of upper income people.”

At a town hall event at a high school gymnasium in Dubuque, Iowa, Warren defended her plan, saying: "All I can say is that employers will pay the same as they’re paying currently under Obamacare. In fact, they pay a little bit less. We stabilize it at 98% of what they’re paying right now and they won’t have to have HR departments that are wrestling with insurance companies. So this is something that’s going to help employers."

When asked about Sanders' criticism, Warren later told reporters on Sunday: "Bernie may have a different vision of how to pay for it, but let's be really clear, Bernie and I are headed in exactly the same direction."

Of note: The two candidates spoke on the phone about Warren's plan after its release, according to ABC.

Go deeper: How middle class workers will pay for Medicare for All