WASHINGTON (AP) — Medicare’s payment system, the unseen but vital network that handles 100 million monthly claims, could freeze if President Barack Obama’s health care law is summarily overturned, the administration quietly informed the courts.

Although Obama’s overhaul made significant cuts to providers and improved prescription and preventive benefits, Medicare was overlooked in Supreme Court arguments that focused on the law’s controversial requirement that all individuals carry health insurance.

Havoc for Medicare could have repercussions as both parties avidly court seniors in this election year and as hospitals and doctors increasingly complain the program doesn’t pay enough.

Last year, in a lower court filing, Justice Department lawyers said reversing Medicare payment changes “would impose staggering administrative burdens” on the government and “could cause major delays and errors” in claims payment.