A public plan option is needed to keep the health insurance market competitive, the president said in remarks at a town hall meeting in Annandale, Virginia.

“This public option is important because if the private insurance companies have to compete, it will keep them honest and help keep prices down,” he said.

Commercial insurers have criticized the proposal, warning that a public plan could drive private insurers out of the market, eventually resulting in a single-payer system.

Obama also said a primary goal of reform is to expand coverage to those who now can’t afford it.

“This is a moral and economic imperative, because we know that when someone without health insurance is forced to get treatment at the [emergency room], all of us end up paying for it—to the tune of about $1,000 per person,” he said.

Turning to how to pay for the cost of subsidizing premiums for the lower-income uninsured, Obama said one revenue source would be a reduction of government subsidies paid to insurers who provide coverage to Medicare-eligible retirees through Medicare Advantage plans.

“We are on track to spend $177 billion over the next decade in unwarranted subsidies to insurance companies that add nothing to care. … Those are your tax dollars, and you deserve better in return. That’s why we’ll direct those resources toward lowering costs, expanding coverage and improving quality for all Americans,” he said.