NEW YORK (AP) - A record 12 percent of homeowners with a mortgage are behind on their payments or in foreclosure as the housing crisis spreads to borrowers with good credit. And the wave of foreclosures isn't expected to crest until the end of next year, the Mortgage Bankers Association said Thursday.

The foreclosure rate on prime fixed-rate loans doubled in the last year, and now represents the largest share of new foreclosures. Nearly 6 percent of fixed-rate mortgages to borrowers with good credit were in the foreclosure process.

At the same time, almost half of all adjustable-rate loans made to borrowers with shaky credit were past due or in foreclosure.

The worst of the trouble continues to be centered in California, Nevada, Arizona and Florida, which accounted for 46 percent of new foreclosures in the country. There were no signs of improvement.

The pain, however, is spreading throughout the country as job losses take their toll. The number of newly laid off people requesting jobless benefits fell last week, the government said Thursday, but the number of people receiving unemployment benefits was the highest on record. These borrowers are harder for lenders to help with loan modifications.

President Barack Obama's recent loan modification and refinancing plan might stem some foreclosures, but not enough to significantly alter the crisis.

"It may be too much to say that numbers will fall because of the plan. It's more correct to say that the numbers won't be as high," said Jay Brinkmann, chief economist for the Mortgage Bankers Association.