NEW YORK, July 17 (Reuters) - S&P 500 stock index futures extended losses on Friday on caution over how long the market's recent run-up would last, following General Electric Co and Bank of America Corp quarterly results.
* "The bar for expectations is higher, and that's one of the reasons I'm not seeing an explosive move here pre-market," said Craig Peckham, equity trading strategist at Jefferies & Company in New York. "It's going to be hard to add onto the big gains we've had this week."
* In Thursday's trading Wall Street held to a fourth-straight day of gains.
* S&P 500 futures were 4 points lower 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 6 points, and Nasdaq 100 futures shed 1.75 points.