05.07.12 Medicare's payment system, the unseen but vital network that handles 100 million monthly claims, could freeze up if President Barack Obama's health care law is summarily overturned, the administration has 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 individuals carry health insurance.

Yet 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. In papers filed with the Supreme Court, administration lawyers have warned of "extraordinary disruption" if Medicare is forced to unwind countless transactions that are based on payment changes required by more than 20 separate sections of the Affordable Care Act.