WASHINGTON — The Trump administration asked a federal appeals court on Monday to delay ruling on a lawsuit that could determine whether the government will continue paying subsidies under the Affordable Care Act to health insurance companies for the benefit of low-income people — effectively prolonging uncertainty that is already rattling the health law.

The request could further destabilize insurance markets as insurers are developing rates and deciding whether to participate in 2018.

Insurers are supposed to submit their proposals to the federal government by June 21 and have already filed rate requests with several states. Loss of the cost-sharing subsidies, they say, could lead them to increase premiums by 15 percent to 20 percent or more, on top of any increases they might seek for other reasons.

In recent statements, the administration has not made any commitment to pay the subsidies beyond this month.