* U.S. fiscal cliff concerns overshadow Greek debt deal
* U.S. Oct durable goods orders unchanged; consumer confidence on tap
* Futures: S&P up 1.3 pts; Dow down 9 pts, Nasdaq up 5.75 pts
By Angela Moon
NEW YORK, Nov 27 (Reuters) - U.S. stock index futures were little changed on Tuesday as worry over the threat to the economy posed by the "fiscal cliff" offset optimism from a deal to ease Greece's debt burden.
Market sentiment improved after European finance ministers and the International Monetary Fund clinched agreement late on Monday on reducing Greece's debt in a breakthrough to release urgently needed loans to keep Greece from defaulting.
But as Democrats and Republicans in Washington prepared to resume budget negotiations, futures cut gains to trade flat and the market reverted to a cautious stance.
S&P 500 futures were up 1.3 points and in line with fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures fell 9 points, while Nasdaq 100 futures were up 5.75 points.
As of Monday's close, the S&P 500 was holding above the 1,400 level it retook last week. But volume continued to be weak as traders awaited any advance in talks between the Obama administration and Congress to avert a series of spending cuts and tax increases scheduled to begin next year. Last week, the broad index rose nearly 4 percent.
"Advancing volume trends have failed to surge during the S&P 500's 4 percent bounce from its Nov. 16 low, suggesting recent strength can be attributed to a lack of selling pressure rather than fresh buying demand," said Ari Wald, analyst at the PrinceRidge Group in New York.
"We would like to see this spread turn positive to confirm an upward S&P 500 reversal," he said.
Government data on October durable goods orders showed a gauge of planned spending by businesses increased by the most in five months. But a fourth straight month of declines in shipments underscored the damage that fears of tighter fiscal policy next year are having on the economy. Market reaction to the Commerce Department was muted.
Standard & Poor's releases its S&P Case/Shiller Home Price Index for September at 9 a.m. (1400 GMT). Economists expect an adjusted 20 city index to rise 0.4 percent, versus a 0.5 percent increase in the previous month.
Conference Board releases November consumer confidence at 10 a.m. (1500 GMT). Economists expect a reading of 73.0, compared with 72.2 in October.
ConAgra Foods Inc will acquire Ralcorp, the largest private label food manufacturer in the U.S. for about $6.8 billion.
ConocoPhillips' partners in Kazakhstan's Kashagan field have 60 days to exercise pre-emption rights to prevent India's ONGC Videsh from buying an 8.4 percent stake in the project held by the U.S. company, the Indian firm's managing director said.
Europe is preparing to follow the United States in delaying the introduction of stricter rules on bank capital, while it lobbies for a rethink of the U.S. stance, EU sources said.
However, the head of the Basel Committee at the Bank of International Settlements told Reuters on Tuesday that the introduction of stricter capital rules for banks will go ahead as planned on Jan. 1.