WASHINGTON - A growing share of home sales are from foreclosures, especially in states hardest hit by the housing bust. In some parts of California lately, nearly 50 percent of home sales come from foreclosed houses.

The trend, which is putting additional downward pressure on home prices, is most notable there and in Nevada, Colorado, Tennessee and Michigan. But it is also evident in Florida, Georgia, Ohio and Arizona, according to an Associated Press comparison of 2007 sales and foreclosure data. In Nevada, for example, 17.5 percent of home sales were from foreclosures, more than quadruple the number in 2006.

The growing proportion of foreclosure sales is both a symptom and cause of worsening conditions in the weakest housing markets, real estate experts say. Homeowners who are not on a deadline to sell are yanking their properties off the market, and this means the remaining inventory is increasingly held by banks eager to unload foreclosed properties at fire-sale prices rather than carry the costs on their books.

As a result, property values and local tax revenues are suffering, especially in neighborhoods with many minority residents, for whom lending standards were weakest, consumer advocates say.

"There is a real complacency, or an underappreciation of how bad this is," said Ramsey Su, an investor and former real estate broker in San Diego who regularly combs through the local sales database to asses the impact of foreclosure sales.

Reacting to such concerns, the Bush administration and lenders, including Bank of America Corp. and Citigroup, unveiled a plan Tuesday to give seriously delinquent borrowers a 30-day break from foreclosure while lenders try to work out a way to make the mortgage more affordable.

Foreclosure Analysis

AP's foreclosure analysis compared the annual rate of existing home sales in the third quarter of 2007 - the most recent quarter available from the National Association of Realtors - with foreclosure sales data provided by RealtyTrac Inc. of Irvine, Calif.

The analysis found:

•In Colorado, foreclosure sales accounted for 15.6 percent of home sales in 2007, up from 10 percent in 2006.

•In California, the number jumped to 11.3 percent from 3.7 percent.

•In Tennessee, it rose to 10.6 percent from 5.2 percent, and in Michigan it climbed to 9.3 percent from 4.9 percent.

•Nationwide, including Washington, D.C., foreclosure sales grew to 4.7 percent of existing home sales, up from 3.3 percent in 2006.

Comparable data were not available for South Dakota and New Hampshire.

The analysis underscores that the housing bust is having the most severe impact in areas where lending standards were the loosest, or where the economy is especially weak. In 18 states - including places as diverse as Maine, New Mexico and Kansas - foreclosure sales made up less than 2 percent of total sales.

Lax lending standards, which were especially prevalent in formerly booming housing markets in California and Nevada, allowed borrowers to buy far more expensive houses than they could afford in the boom years, and now defaults are surging. Highly discounted foreclosure sales also can make it tougher for borrowers to refinance into more affordable loans if their property value falls, which could lead to more foreclosures and lengthen the housing crisis.

Trend Accelerating

Thomas Blanchard, who sells bank-owned properties in Las Vegas, said the trend has accelerated the past two months. He estimates that 60 percent of properties on the market there are in foreclosure.

"The only people that you have in our market here in Las Vegas are the people that have to sell," he said.

The same is true in parts of California. In December, 46 percent of homes sold in the Sacramento area and 31 percent in the San Diego area went through foreclosure, up dramatically from about 4 percent a year earlier, according to San Diego-based DataQuick Information Systems, a real estate information firm.

Banks, faced with mounting costs of holding properties, are cutting prices. The average price of a foreclosure sale nationwide dropped about $1,000 last year to about $226,000, according to RealtyTrac.

While foreclosure sales are bad news for homeowners in neighborhoods with high foreclosure rates, they are a boon for well-financed buyers looking for properties at bargain prices. And in broad terms, economists view them as part of getting back to more realistic prices after years of excess.

Alejandro Diaz-Bazan, who sells foreclosed properties in Miami, said banks seeking to unload foreclosed properties look for buyers who can close deals quickly, and therefore need to have a hefty down payment. This month, Diaz-Bazan said a European client bought two foreclosed condominiums as an investment.

"The bank really is out to move them, to liquidate them," Diaz-Bazan said. Despite the downward pressure on prices, he said, "property prices in Miami have not dropped enough" for the market to rebound.

More than half of houses sold in San Diego last month were bank-owned or short sales, in which a lender agrees to accept less than the value of the mortgage to avoid foreclosure. The number was up dramatically from 26 percent in August, according to Su's calculations.