Enough insurers are planning to sell coverage on the Affordable Care Act's insurance exchanges next year to keep those markets working in most parts of the country.

Competition has dwindled, however, and another round of steep price hikes is expected to squeeze consumers who don't receive big income-based tax credits to help pay their bill.

Health insurers had until Wednesday to declare whether they planned to sell coverage next year on the exchanges in most states. Actual participation and final rates won't be set until later in the year.

The consulting firm Avalere expects more than 40 percent of U.S. counties to have only one insurer selling coverage on the exchange in 2018. Early plans filed by many insurers include premium increases of well over 20 percent.