Former U.S. president Jimmy Carter says he supports a single-payer health-care system -- a view that was possibly reinforced by his hospital experience after he collapsed in Canada 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 his party 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 of how he 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.

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.

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

With files from The Associated Press