President Donald Trump, a Republican, has repeatedly threatened to stop the payments, which are made directly to insurance companies to help cover out-of-pocket medical expenses for low-income Americans enrolled in individual healthcare plans under the Affordable Care Act (ACA). The payments are estimated to amount to $7 billion in 2017.

The Centers for Medicare and Medicaid Services also said on Wednesday that two counties were projected to have no insurer in 2018 selling plans on the individual market created under former Democratic President Barack Obama's healthcare policy, down from 40 earlier this year.

Both announcements could bring some short-term stability to insurance markets, but the long-term outlook is uncertain, said Cynthia Cox, policy researcher and associate director at the nonprofit Kaiser Family Foundation.