* Apple up after Topsy buy, UBS upgrade
* Cyber Monday sales appear strong
* Yum Brands November China sales flat
* Futures up: Dow 64 pts, S&P 5.8 pts, Nasdaq 5.25 pts
By Chuck Mikolajczak
NEW YORK, Dec 3 U.S. stock index futures fell on Tuesday, indicating the S&P 500 may fall for a third consecutive day on concerns a scale-back in stimulus by the Federal Reserve may be on the horizon.
* The benchmark S&P index fell on Monday as stronger than expected data on manufacturing and construction spending prompted speculation the Fed may lean towards scaling back its stimulus of $85 billion in monthly bond purchases.
* While virtually all market participants accept the central bank will begin to trim the stimulus at some point, the timing remains in question, with many analysts expecting the announcement in March.
* The Fed has said it would begin to slow the program when certain economic measures meet its targets. The economic calendar is packed this week with data that may provide some insight, culminating with the November payrolls report on Friday.
* S&P 500 futures fell 5.8 points and were below 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 64 points and Nasdaq 100 futures lost 5.25 points.
* After a disappointing to start to the holiday shopping season, U.S. online sales are expected to hit $2 billion on "Cyber Monday," for the first time since the data firm comScore began tracking such information. Amazon.com Inc shares slipped 0.2 percent in light premarket trade.
* Apple Inc has acquired social media search and analytics startup Topsy, an unusual purchase for a hardware-focused company that has made few forays into social networking. The iPhone maker was subsequently upgraded to a "buy" rating by UBS. Apple shares were up 1.1 percent to $557 in premarket trade.
* Yum Brands Inc said November sales at established KFC restaurants in China, its top market, failed to grow despite a successful half-priced chicken promotion, and it forecast a return to earnings per share growth in 2014.
* European stocks edged down to one-week lows, led by miners after strong U.S. data heightened concern the Federal Reserve will scale back stimulus sooner rather than later.
* Asian shares fell as a batch of upbeat U.S. economic data on Monday suggested the Federal Reserve may tilt towards reducing its stimulus soon.