"I don't want to start over," he said Friday in Dover. "How many of you out there have had someone you've lost to cancer? Or cancer yourself? No time, man. We cannot have a hiatus of six months, a year, two, three, to get something done. People desperately need help now."
"At a time when Donald Trump and the health insurance industry are lying every day about Medicare for all, I would hope that my fellow Democrats would not resort to misinformation about my legislation," Sanders said in the statement.
He said under his proposal, "over a four-year period, we will transition to a system in which Medicare is expanded to cover every man, woman, and child in the country."
"It is preposterous to argue that as we expand Medicare for All that people with cancer and other illnesses will not get the care that they need," Sanders said. "In fact, under Medicare for All, the good news is that we will end the horror of millions of people going into bankruptcy and financial distress simply because they need hospital care for serious conditions."
Biden was similarly critical of Medicare for all proposals again Saturday morning in Atkinson, saying his own proposal for a public option would cost $750 billion over 10 years.
"But it doesn't cost $3 trillion, and it can be done quickly," he said. "And I don't know why we would get rid of what, in fact, was working, and move to something totally new."
Sanders is targeting Biden -- but Biden's criticism of Medicare for All has also been directed at other Democratic candidates who have endorsed Sanders' plan.
On Friday night in Portsmouth, New Hampshire, Biden said Sanders is the only Democratic candidate who has been forthcoming about the costs and ramifications of Medicare for All.
"Bernie's been very honest about it. He said you're going to have to raise taxes on the middle class. He said it's going to end all private insurance. I mean, he's been straightforward about it. And he's making his case," Biden said.
He was asked if other Democrats are doing so, as well.
"Well, so far, not. So far, not. They may," Biden said.
Among the Democratic 2020 front-runners, Biden is the only opponent of moving to a single-payer health plan in which all Americans would be enrolled in a government-run program like Medicare, paying higher taxes instead of health care premiums, deductibles and copays.
Sanders has long advocated such a plan, and in the first Democratic presidential debate, Sen. Elizabeth Warren of Massachusetts offered her most full-throated endorsement yet of Medicare for All.
Several other Democratic candidates, including Warren, Harris and Sens. Cory Booker of New Jersey and Kirsten Gillibrand of New York, co-sponsored Sanders' 2017 Medicare for All bill and have endorsed the policy as they seek the presidential nomination.
Asked by CNN if Harris has been forthcoming enough about her ideas to end private insurance, Biden said: "I'll let you guys make that judgment."
Biden called single-payer health plans "hard to explain" to voters worried about what drastic changes to their insurance would mean.
When asked whether Democrats can win the White House with a nominee who advocates Medicare for All, Biden paused for a moment, finally saying: "The answer is, I think what the American people are looking for is something that gives than surety."
"I'm not saying that people will necessarily vote against it," he said. "Thus far, I think it gets hard to explain it and indicate how you're going to be OK; there's going to be nothing missing, as my mother would say, between the cup and the lip."