"You don't know. Nobody knows. This is impossible to predict," Sanders told CBS News' Norah O'Donnell.
"Do you know exactly what health care costs will be, one minute, in the next 10 years if we do nothing?" Sanders said. "It will be a lot more expensive than a Medicare-for-all single-payer system."
Sanders' campaign promises of taxpayer-funded health care and college tuition has an estimated price tag of $60 trillion over 10 years, O'Donnell said.
"Sure, it might be a hard sell," Sanders said. "The American people want a health care system that works for them, not for huge profits for the drug companies who are ripping us off every day and the insurance companies. At the end of the day, we will create more jobs. Will there be some job loss? Yes, there will. We're gonna create more jobs. We need more doctors. We need more nurses. We need more psychologists and psychiatrists to help us deal with the opioid epidemic. There'll be a net plus of jobs."
Meanwhile, Sanders' rival Sen. Elizabeth Warren pledged in November not to raise taxes on the middle-class to fund her sprawling, $52 trillion Medicare-for-all plan. She was facing mounting pressure from political opponents to flesh out her proposal to overhaul American health care.
FOX Business' Megan Henney contributed to this report.