Kentucky's new Medicaid commissioner says the cost to run the state health insurance program will jump 20 percent to more than $3.7 billion over the next two years, calling into question its sustainability long term.

Former Democratic Gov. Steve Beshear expanded Kentucky's Medicaid program under the federal Affordable Care Act. The expansion brought in an additional 428,000 people, far more than state officials had predicted.

The promotion of the new program also brought in about 60,000 people who qualified for the traditional Medicaid program but had not signed up for the service. Medicaid Commissioner Stephen Miller said those people cost about $124 million a year.

Republican Gov. Matt Bevin has promised to repeal the expanded Medicaid program and replace it with something else, possibly a system that would require people to pay a small premium.