Premiums for ObamaCare's benchmark silver plans will increase by an average of 15 percent in 2018, the Congressional Budget Office (CBO) estimated in a new report released Thursday.
CBO blamed the premium hikes on "short-term market uncertainty."
Insurers have pleaded for more certainty on key ObamaCare payments called cost-sharing reduction subsidies, which reimburse them for giving discounts to low-income patients.
The Trump administration has made the payments on a month-to-month basis, but insurers want them funded on a long-term basis.
The Senate's Health Committee is working on a bipartisan bill that would fund the payments at least through 2018, but it's unclear if a deal can be reached between Democrats and Republicans.
They're working on a short timeline, however.
Insurers must sign contracts by Sept. 27 to be able to participate in the ObamaCare markets next year.
Also contributing to higher premiums in 2018, CBO said, is a higher percentage of the population living in areas with only one ObamaCare insurer.
Several insurers have said they won't participate in the markets next year, leaving many counties with only one insurer.
Uncertainty in the market will likely be resolved by 2019, CBO said, with premiums expected to be lower.
The CBO also estimated that enrollment will increase from 10 million this year to 11 million next year.
That growth is limited, however, because of premium increases, the Trump administration's cuts in ObamaCare advertising and outreach funding, and a shorter enrollment period, CBO said.