"People have made some pretty compelling arguments to me that if we want to have a system that drives down costs for everybody, then we've got to have healthier people not opt out of the system," the president told ABC News.
Earlier this month in a letter to congressional leaders working on the reform legislation, Obama said he would consider supporting such a measure, if it has room for exemptions for small businesses and individuals who cannot afford the premiums.
With the health care debate ramping up, with Republicans assailing Democrats for the high price tag and a public option plan, Obama's ratings on the subject slipped slightly in the latest ABC News/Washington Post poll.
Only 53 percent of Americans approve of Obama's handling of health care while 39 percent disapprove of it, up from 29 percent who disapproved in April, according to the poll.
Concluding the health care forum, Obama expressed optimism that reform is possible.
"If the American people get behind this, this is going to happen," the president said.
ABC News' Z. Byron Wolf contributed to this report.