Expect Obamacare prices to rise faster in 2017 than in years past, says a new nonpartisan report from the Kaiser Family Foundation.

The most popular type of insurance plan, the lowest-cost, mid-grade "silver" plans, will be an average of 10 percent more expensive next year in major cities in 13 states and the District of Columbia, the foundation found. This year, plans got just 5 percent more expensive on average in those same areas.

The data are incomplete and not final, as more states have yet to publish proposed insurance rates and insurers can still forego hikes later this year. But at least for now, they indicate that plans offered on the Affordable Care Act's marketplaces are getting more costly more quickly.

That could be partly due to the expiration of a program which transferred funds to insurers facing steep losses. The extra money helped pad insurers for the first couple years of the marketplaces, but now they're more likely to try to recover from the losses by raising premiums.

"Several factors will influence how premiums will change in 2017, and there is reason to believe that increases will be higher than in recent years," the report says.

Kaiser also found that fewer insurers are selling plans on the Obamacare exchanges. An average of 5.5 insurers will offer coverage in 14 states analysts looked at, slightly less than participation in 2015 and 2016 and equal to the number participating in 2014.

The findings are likely to fuel Republican complaints that President Obama's healthcare law isn't providing affordable insurance coverage or helping to tamp down rising costs. But the Obama administration responded to the Kaiser report by noting that the majority of Obamacare customers will qualify for subsidies to help pay for their plans.

"Last year, HealthCare.gov premiums increased an average of just $4 per month after shopping and tax credits, and consumers will benefit from shopping and tax credits again this year," said Benjamin Wakana, a spokesman for the Department of Health and Human Services.

"This is just the beginning of the rates process, and despite headlines suggesting double digit increases, proposed rates aren't what most consumers actually pay because the vast majority of consumers qualify for tax credits that reduce the cost of coverage below the sticker price, and people can shop around and find coverage that fits their needs and budget," Wakana added.