UnitedHealth, the nation’s biggest health insurer, will cut its participation in public health insurance exchanges to only a handful of states next year after expanding to nearly three dozen for this year.

CEO Stephen Hemsley said Tuesday that the company expects losses from its exchange business to total more than $1 billion for this year and last. He added that the company cannot continue to broadly serve the market created by the Affordable Care Act’s coverage expansion due partly to the higher risk that comes with its customers.