Health insurer Centene Corporation will be selling plans on the Obamacare exchange in Missouri in 40 counties that will cover customers in 2018, including the 25 counties that were facing the prospect of having no insurer to buy tax-subsidized coverage next year.

The company also announced this month that it planned to offer plans on the exchange in Kansas and Nevada. It had announced its plans for Missouri as well, but Friday's announcement solidifies its intention to fill the "empty counties" that are set to be vacated by Blue Cross Blue Shield.

The state's insurance commissioner said in a statement that it had been working to fill the empty counties.

"Our collaboration with Centene and other local stakeholders reflects the strength and leadership of state-based regulation in solving problems for our fellow citizens," said Chlora Lindley-Myers, Missouri's insurance director.

The exchanges allow low- and middle-income people to purchase health insurance that is subsidized by the federal government. Centene is known for its participation in the Medicaid program, which largely covers low-income people.

"Centene is proud to be headquartered in the state of Missouri. Our local Missouri health plan, Home State Health, has been proudly serving Medicaid members since 2012," Michael Neidorff, Centene's chairman, president and CEO, said in a statement.

Amid uncertainty about the future of Obamacare as Republicans in the Senate work to repeal and replace portions of the law, several insurers have said they plan to exit states next year unless circumstances change. Aetna, Humana and UnitedHealth Group are among those that have either completely pulled out of the exchange business or have only a few markets left. According to the Kaiser Family Foundation, which conducts research on healthcare, 36 U.S. counties are still facing the prospect of having no insurers to receive tax-subsidized plans next year, in Ohio, Nevada and Indiana. Currently, 23,393 customers are signed up for these plans.

Insurers in large part have said that they have lost money on the exchanges, in which a disproportionate number of sicker, older enrollees have signed up. They also face uncertainty about whether the Trump administration will continue to pay out billions of dollars in cost-sharing reduction subsidies that help them reduce out-of-pocket costs to customers, as well as whether the administration will enforce Obamacare's law that fines people if they don't have insurance.