(AP) — UnitedHealth, the nation’s biggest health insurer, says it will remain in public health insurance exchanges in only a handful of states next year after expanding to 34 this year.

CEO Stephen Hemsley says the company cannot continue to broadly serve the market created by the Affordable Care Act’s coverage expansion because of the higher risk that comes with its customers.

UnitedHealth Group Inc. has estimated that it could lose as much as $475 million on its public exchange business this year and expects losses from its exchange business to total more than $1 billion for this year and last.