By Edward Krudy
NEW YORK (Reuters) - U.S. stock index futures rose on Monday as Wall Street looked to extend three weeks of gains at the start of a holiday-shortened week expected to see thin trading.
* Stocks have rallied strongly this month, with the S&P 500 up more that 5 percent in December alone and at a two-year high. Some expect the market to grind higher to year-end. Others say equities are overbought and warn of profit-taking.
* "Although investor participation may be limited, the outlook is for a strong finish into year-end," said Andre Bakhos, director of market analytics at Lek Securities in New York. "Any news that would move the market lower would have to be of a high magnitude."
* S&P 500 futures rose 5.7 points and were above 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 gained 37 points, while Nasdaq 100 futures fell 1 points.
* Markets will be closed on Friday in observance of the Christmas holiday the following day.
* Underscoring expectations of a strong holiday spending season, U.S. online sales are up 12 percent to $27.5 billion so far this holiday shopping season, compared with a year ago, according to research firm comScore
* Investor nerves were rattled by possible escalating tensions on the Korean peninsula after South Korea held live firing drills in a disputed area.
* Also in focus will be Adobe Systems Inc
* In company news, U.S. energy major Chevron Corp
* Genzyme Corp
* Food and beverage company Sara Lee Corp
* Google Inc
* In European equity markets, the FTSEurofirst 300 <.FTEU3> rose 1 percent in early trade, with energy shares supported by firmer crude prices as cold weather in Europe and parts of the United States boosted demand for heating fuel.
(Reporting by Edward Krudy; editing by Jeffrey Benkoe)