WASHINGTON (December 20, 2012)--Higher Medicare premiums are likely for many seniors if there's a budget deal between President Barack Obama and Republicans in Congress.

Both sides agree on the expansion of a current, little-known law so more retirees who are considered well off by the government are required to pay higher premiums for outpatient and prescription coverage.

That would raise $20 billion or more over 10 years, but it could come as a shock to many seniors who consider themselves solidly middle-class, and by no means wealthy.

Right now about 5 percent of Medicare beneficiaries pay higher premiums, but that number could grow to 25 percent if the change goes through.

The higher premiums kick in for individuals making more than $85,000 and couples earning above $170,000.