* S&P 500 little changed after best two-day run in a month
* GM surges, will buy back shares from Treasury
* Oracle gains as software sales boost profit
* Dow down 0.1 pct, S&P off 0.2 pct, Nasdaq up 0.1 pct
By Leah Schnurr
NEW YORK, Dec 19 (Reuters) - U.S. stocks barely budged on Wednesday as stalled "fiscal cliff" negotiations gave investors little reason to keep buying following the best two-day rally for the S&P 500 in a month.
General Motors bucked the overall weakness to surge 8 percent after the company said it will buy back 200 million of its shares from the U.S. Treasury, which plans to sell the rest of its GM stake over the next 15 months. GM shot up 8 percent to $27.52.
Talks on avoiding the tax hikes and spending cuts that are set to come into effect in the new year are at a standstill amid a Republican plan to vote on extending tax cuts for all but those making $1 million or more, senior administration officials said.
President Barack Obama said he is still optimistic a deal is possible and that he would like to get it done before Christmas.
Investors are concerned that the fiscal cliff could send the U.S. economy back into recession, though most expect an agreement will be reached eventually.
Investors are positioning for a possible retreat once a deal is announced as market participants may choose to sell on the news after the recent run-up, said Alan Lancz, president of Alan B. Lancz & Associates Inc, in Toledo, Ohio.
If expectations of a deal start to buoy the market, "we'd be more inclined to take profits than chase these valuations now," Lancz said.
The Dow Jones industrial average slipped 14.45 points, or 0.11 percent, to 13,336.51. The Standard & Poor's 500 Index shed 3.06 points, or 0.21 percent, to 1,443.73. The Nasdaq Composite Index added 1.75 points, or 0.06 percent, to 3,056.28.
Markets have been lifted in recent weeks by any signs that an agreement between policymakers over the budget may be reached, with banks and energy shares - groups that outperform during periods of economic expansion - leading gains.
The S&P 500 added 2.3 percent over the past two sessions, the first time it has marked two straight days of 1 percent gains since late July. Still, trading has been light ahead of the holidays, and with investors' focus on the budget talks.
Defensive sectors led the downside on Wednesday, with the S&P utilities sector index slipping 0.5 percent.
Gains in technology shares boosted the Nasdaq after Oracle reported earnings that beat expectations on strong software sales growth. Oracle jumped 4 percent to $34.19, while the S&P tech sector index was up 0.1 percent.
Knight Capital Group Inc climbed 5.7 percent to $3.52 after it agreed to be bought by Getco Holdings in a deal valued at $1.4 billion. The stock, which nearly collapsed after a trading error in August, remains down about 70 percent so far this year.
An index of housing stocks gained 0.2 percent after data showed homebuilding permits touched their highest level in nearly 4-1/2 years in November. The PHLX housing index has surged nearly 70 percent this year as the housing market has turned the corner.