WASHINGTON — Sales of existing homes sank unexpectedly last month to the lowest level in nearly 12 years as potential buyers worried about their jobs and awaited details of President Barack Obama's plans to stabilize the housing market.

But the banking industry's teetering fortunes and mounting job losses could stall any recovery. Falling prices and low mortgage rates don't make much of a difference for people who are out of work — or fearful of losing their jobs.

The most optimistic outlook is for a spring revival as home prices plummet. Government officials, hoping to spur demand, on Wednesday rolled out the details of a new $8,000 tax credit for first-time buyers. About 40 percent of all home sales last year were from first-time buyers.

Treasury Secretary Timothy Geithner said the tax credit should help provide an "immediate response to the current crisis."

Sales of existing homes fell 5.3 percent to an annual rate of 4.49 million last month, from 4.74 million in December, the National Association of Realtors said Wednesday. It was the weakest showing since July 1997. And some analysts don't see sales bottoming out until later this year as prices sink further. Economists had expected sales to rise to an annual pace of 4.79 million homes.