The U.S. House and U.S. Department of Health & Human Services on Monday asked a federal appeals court to freeze for another 90 days a dispute over billions of dollars in insurance industry subsidies under the Affordable Care Act, a delay that could further unnerve the health insurance markets.

The lawfulness of the subsidies — which the government pays to health insurers as part of a cost-sharing program to reduce premiums and other out-of-pocket expenses for low-income consumers — is the centerpiece of a case in the U.S. Court of Appeals for the D.C. Circuit. An estimated 6 million consumers participate in the cost-sharing program.

The D.C. Circuit in December put the case on hold to allow the U.S. House of Representatives, which sued over the propriety of the subsidies, and the incoming Trump administration to decide whether and how to resolve the dispute. The court set a May 22 deadline for the lawyers to advise the panel judges on the next steps in the litigation.