* S&P/Case Shiller data tops expectations
* Obama heads back to Washington after vacation
* Indexes: Dow up 0.12 pct, S&P down 0.02 pct, Nasdaq down 0.06 pct
NEW YORK, Dec 26 (Reuters) - U.S. stocks were little changed on Wednesday ahead of the resumption of negotiations over the "fiscal cliff".
President Barack Obama, after vacationing in Hawaii, is due back in Washington early Thursday for a final effort to negotiate a deal with Congress to avert or at least postpone the cliff, a series of tax increases and government spending cuts set to begin next week.
"There is so little out there in terms of driving the market, it is so quiet and the horizon is just so blank, the only thing that could really bring the market any kind of movement is something as symbolic as the President's early return to Washington from his vacation in Hawaii," said Peter Kenny, managing director at Knight Capital in Jersey City, New Jersey.
"No one is hitting the panic button yet and part of that lack of panic selling is the notion that the Street is getting comfortable with the likelihood of a temporary fix for the fiscal cliff - something that gets us over the date of Jan. 1 in a way where it can be re-addressed."
A Republican plan that failed to gain traction last week triggered the recent decline in the S&P 500, highlighting market sensitivity to headlines centered around the talks.
Data showed U.S. single-family home prices rose in October, reinforcing the view the domestic real estate market is improving, as the S&P/Case Shiller composite index of 20 metropolitan areas gained 0.7 percent in October on a seasonally adjusted basis.
The Dow Jones industrial average gained 15.34 points, or 0.12 percent, to 13,154.42. The Standard & Poor's 500 Index shed 0.31 points, or 0.02 percent, to 1,426.35. The Nasdaq Composite Index dropped 1.92 points, or 0.06 percent, to 3,010.68.
The benchmark S&P index is up 13.5 percent for the year, and has recouped nearly all of the losses suffered in the wake of the U.S. elections, when the fiscal cliff concerns moved to the forefront of investors' focus.
Retailers will be in focus as data on the holiday shopping season begins to come in. Holiday-related sales rose 0.7 percent from Oct. 28 through Dec. 24, compared with a 2 percent increase last year, according to data from MasterCard Advisors SpendingPulse.
"The broad brush was Christmas wasn't all that merry for retailers and you have to ask what those margins look like if the top line didn't meet their expectations," said Kim Forrest, senior equity research analyst at Fort Pitt Capital Group in Pittsburgh.
The Morgan Stanley retail index slipped 0.8 percent.
China's Sinopec Group and ConocoPhillips will research potentially vast reserves of shale gas in southwestern China over the next two years, state news agency Xinhua reported. Conoco shares edged up 3 cents to $58.47.
An outage at one of Amazon.com Inc's web service centers hit users of Netflix Inc's streaming video service on Christmas Eve and was not fully resolved until Christmas Day, a spokesman for the movie rental company said on Tuesday.
Amazon lost 1 percent to $256 and Netflix shed 0.7 percent to $89.57.