MIAMI — A record 2.8 million households were threatened with foreclosure, and that number is expected to rise this year as more unemployed and cash-strapped homeowners fall behind on their mortgages.

The number of households that received a foreclosure-related notice rose 21 percent from 2008, RealtyTrac Inc. reported Thursday. One in 45 homes were sent a filing, which includes default notices, scheduled foreclosure auctions and bank repossessions.

Stemming the tide of foreclosures is an important step for the real estate market and the economy to recover. Because foreclosures are usually sold at heavy discounts they can lower the value of surrounding properties. Cities lose property tax dollars from empty foreclosures and declining home values, straining local economies. Home prices have stabilized in some cities, but are still down 30 percent nationally from mid-2006.

The foreclosure crisis isn't letting up. Between 3 and 3.5 million homes are expected to enter some phase of foreclosure this year, said Rick Sharga, senior vice president of Irvine, Calif.-based RealtyTrac, which began tracking the data five years ago. "It was bad, but it could have been much worse, and it probably should have been worse," Sharga said.

Economic issues, such as unemployment or reduced income, are expected to be the catalysts for foreclosures this year. Homeowners with good credit who have conventional, fixed-rate loans are the fastest growing group of foreclosures.