Former U.S. president Jimmy Carter says he supports a single-payer health-care system — an opinion that appears to have been reinforced by his hospital experience in Winnipeg earlier this year.

Carter told college students in Atlanta on Wednesday that he proposed a measure as president that would have phased in a "medicare-for-all" structure by extending benefits first to children, then to older Americans as the federal budget allowed.

That did not pass.

He acknowledged the considerable expense of single-payer models and the political risks for U.S. Democrats if they anger the private insurance industry and push the tax hikes necessary to pay for universal coverage.

But the 92-year-old told the students about how he was hospitalized for dehydration in July while working on a Habitat for Humanity project in Winnipeg.

Carter said when he was released, he asked what he owed and was told "zero," adding "the Canadian taxpayers paid for my treatment."

Carter was back at the Habitat for Humanity worksite the next day, where hundreds of volunteers joined the former president and his wife, Rosalynn, to build 25 homes.

Canada does not pay for hospital or medical services for visitors, the Government of Canada's immigration and citizenship website says. Visitors need to get health insurance to cover any medical costs before coming to the country.

The U.S. has a patchwork system that's mostly private, partly public and covers the vast majority of Americans. When Barack Obama took office, about 84 per cent of Americans had health coverage; the number rose to about 89 per cent under his reform; now the parties are debating next steps.

Some Republicans are still working on bills to pare back Obamacare. Some Democrats want to focus their fight on saving what exists. But others, like Bernie Sanders, want to expand the battle to new terrain: single-payer health care.

Carter told the students that, theoretically, single-payer is "the best system."