UPDATE 2-US home prices fell in December - S&P/Case Shiller

(Adds details from report)

NEW YORK Feb 27 (Reuters) - The prices of existing U.S. single-family houses extended their slide in most regions in December, trimming annual price gains, according to an index of major metropolitan areas released on Tuesday.

The composite month-over-month Standard & Poor's/Case-Shiller Home Price Index of 10 metropolitan areas declined 0.8 percent to 222.01, unchanged year-over-year, S&P said on its Web site.

The composite month-over-month Standard & Poor's/Case-Shiller Home Price Index of 20 metropolitan areas showed a 0.7 percent drop in December, a 203.07 reading, and a 0.5 percent year-over-year gain.

"Annual changes in home prices are either in decline, flat or yielding negative returns across all markets," Robert J. Shiller, chief economist at MacroMarkets LLC, said in a release.

"All metro areas are showing smaller annual returns than those reported for November. The newly published U.S. National Index, which has historically portrayed less volatile increases and declines, joins the other two composites in the steep decline that began in 2005, falling 0.7 percent over the quarter and ending the year at just 0.4 percent annual growth," he said.

The S&P/Case-Shiller U.S. National Home Price Index tracks the value of single-family homes across the country.

Standard & Poor's last week announced an expansion of its S&P/Case-Shiller U.S. Home Price Indexes to add a quarterly gauge of national home prices.

U.S. home prices rose 0.4 percent in the fourth quarter of 2006 compared with the same quarter a year earlier, according to the index. Prices were down 0.7 percent in the fourth quarter from the previous quarter.

The next S&P/Case-Shiller U.S. National Home Price Index will be released the last Tuesday of May.

Joining the ranks for metro areas in negative territory was New York, yielding a negative 0.1 percent annual return. That's in stark contrast to the 15.3 percent gain reported in April 2005, the release said.

While Seattle and Portland have shown some resilience, they continue to experience diminishing but relatively robust returns, ending the year at 12.1 percent and 9.9 percent, respectively.

Eighteen out of the 20 metro areas, as well as the two composites, showed negative returns from those published at the end of the third quarter of last year.

The 20 regions in the broader index are Atlanta, Boston, Charlotte, Chicago, Cleveland, Dallas, Denver, Detroit, Las Vegas, Los Angeles, Miami, Minneapolis, New York, Phoenix, Portland, San Diego, San Francisco, Seattle, Tampa and Washington, D.C.

The index was co-developed by Shiller, also a Yale University economist, who had warned of a house price bubble and predicted in the late 1990s the stock market was driven by excessive speculation.