(CNN) The Trump administration just halted a key set of payments to Obamacare insurers, but it's consumers who could wind up having to foot the bill.

That's because the federal government won't distribute $10.4 billion it was expected to give insurers this fall under the Affordable Care Act's risk adjustment program . The administration said Saturday that it would temporarily suspend the payments because a federal judge earlier this year ruled the program's formula was flawed.

Insurers rely on the funding, which serves as a backstop for those who wind up with a high share of costly enrollees. Under the risk adjustment program, insurers with healthier policyholders contribute money, which is then divvied up among carriers with sicker ones. It's the only remaining risk mitigation program in Obamacare. The other two, which were designed to last only three years, ended after 2016.

The administration's latest effort to undermine the Affordable Care Act comes at a particularly sensitive time for insurers. They are now deciding which exchanges they will participate in next year and what premiums they'll charge. Having a risk adjustment program factors into these calculations.

"This action will significantly increase 2019 premiums for millions of individuals and small business owners and could result in far fewer health plan choices," said Scott Serota, CEO of the Blue Cross Blue Shield Association, which represents 36 independent insurers, many of whom are key players on the exchanges. "It will undermine Americans' access to affordable coverage, particularly those who need medical care the most."

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