Obama says the Medicare trust fund will be in the red and out of money in a decade unless Washington overhauls the system.
Both houses of Congress are grappling with the issue. In opening remarks to the AARP-sponsored forum, Obama said some of the money that's being spent and doesn't improve people's health could be used to bring down costs.
He said: "We've got to get a better bang for our health care dollar."
AARP is an advocacy group for people over the age of 50.