WASHINGTON -- Sen. Bernie Sanders, I-Vt., defended his call for a single-payer 'Medicare for All' program Wednesday, pushing back against criticism from former Vice President Joe Biden and other Democratic presidential candidates who have decried it as unrealistic and overly disruptive.

Without naming his opponents, Sanders argued in a speech at George Washington University that “tinkering” with the health care system was insufficient and that more sweeping measures were needed.

While Biden and others have suggested preserving existing private insurance plans while adding a competing public option, Sanders repeatedly made the case that the health care industry was too compromised by profit-seeking to be trusted with such a large role, listing CEO compensation and pointing to higher prices for care compared to other developed countries.

“The debate we are currently having in this campaign and this country has nothing to do with health care, but it has everything to do with the greed and profits of the health care industry,” Sanders said.

Sanders, a self-described democratic socialist, announced a pledge to not take any contributions from political action committees, lobbyists or executives associated with the insurance or pharmaceutical industries and challenged other candidates to follow suit. Much of the field has forsworn corporate PAC and lobbyist donations in general.

Biden, speaking at an AARP event in Iowa earlier this week, told the audience that “Medicare goes away as you know it” if Sanders were to expand it to all Americans.

In his own speech, Sanders stressed the benefits of Medicare for All for seniors, who would have access to dental, vision and other benefits currently not covered by Medicare and would no longer have to pay premiums.

“Despite what you’re hearing about Medicare for seniors being weakened, the truth is exactly the opposite,” he said. “It will be strengthened.”

Sanders has not specified how he will pay for his plan, which he said Tuesday would cost the government between $30 trillion and $40 trillion over 10 years. But he has conceded middle class taxes will need to go up given its scale, something Biden has attacked him for proposing.

Sen. Kamala Harris, of California, a supporter of Sanders' Medicare for All plan, told CNN this week that she would not raise middle class taxes to pay for it, despite widespread assertions by experts that the proposal is far too large to finance through taxes on the rich alone.

On Wednesday, Sanders sought to reframe the terms of the debate, arguing that people’s existing insurance premiums and deductibles — which would be eliminated entirely under Medicare for All — were “nothing less than taxes on the middle class.”

“My Republican friends and some others seem to think that the American people hate paying taxes but they just love paying insurance premiums,” he said to laughter. “Oh my God, the insurance premium is here, what a wonderful day! Oh wow, let’s celebrate!”

Sanders said his plan would “reduce — let me repeat — reduce overall heath care spending” by empowering Medicare to negotiate lower payment rates for health care providers and for prescription drugs.

Biden’s own plan, released this week, would cost $750 billion over 10 years and increase subsidies to purchase insurance through the Affordable Care Act while giving Americans the choice to buy a public option rather than a private plan.