(Reuters) - The Obama administration has approved plans by Arkansas, Delaware and Pennsylvania to create their own state-based health insurance marketplaces instead of relying on a federal website to enroll residents, a government spokesman said on Tuesday.

The three are among 37 states that rely wholly or in part on the federal HealthCare.gov website to sell health insurance plans and provide government subsidies to families based on income.

If the states proceed with setting up the exchanges, they will join 13 others and the District of Columbia in operating their own marketplaces under President Barack Obama's Affordable Care Act, which is also known as Obamacare.

The approvals from the U.S. Department of Health and Human Services come as the Supreme Court is set to decide later this month whether the states that use HealthCare.gov can continue to receive subsidies from the federal government.

Libertarian opponents of Obamacare brought the case, known as King v. Burwell. They argue that the law only allows for subsidies when a state operates its own exchange.

HHS Secretary Sylvia Burwell sent approval letters to all three states on Monday detailing the timelines for implementing the marketplaces.

Arkansas aims to set up a state-based exchange for small businesses in 2016, with one for individual customers following in 2017. Delaware and Pennsylvania plan to establish state-based exchanges for both markets in 2016.

According to a recent poll by the Kaiser Family Foundation, as many as 55 percent of people in states that use HealthCare.gov said their local leaders should set up an Obamacare exchange if the Supreme Court rules that the federally administered subsidies are illegal.

(Reporting by Kylie Gumpert; Editing by Michele Gershberg and Lisa Von Ahn)