Stock index futures were little changed on Friday, with the Dow on track for a ninth straight week of gains, as investors awaited a key reading on economic growth to see if recent gains could be extended.

The U.S. gross domestic product advanced reading, due at 8:30 a.m. EST (1330 GMT), is seen having risen 3.5 percent in the fourth quarter, more growth than the previous quarter but not enough to significantly lower severe unemployment.

The Dow and the S&P have struggled to advance past major technical levels -- 12,000 for the Dow and 1,300 for the S&P -- with technical measures indicating the market could be overstretched. Still, the Dow was on track to notch its ninth straight week of gains, and the S&P ended at a new 29-month high on Thursday.

Because we've been up so much, the market is vulnerable and the GDP number could be the thing that causes it to tip, said James Dailey, portfolio manager of TEAM Asset Strategy Fund in Harrisburg, Pennsylvania.

Ford Motor Co tumbled 6.3 percent to $17.60 in premarket trading as it reported a steep drop in its quarterly profit after a charge for debt payments. Rival automaker General Motors Co lost 2.1 percent to $37.84 before the bell.

Ford results were pretty ugly, Dailey said, adding that the stock had been adopted by momentum players. Ford shares have risen almost 12 percent from the start of January to the Thursday close.

When that happens you need to have the company beat in the quarter and raise its outlook in order to keep moving higher. When that doesn't happen, the stock gets pummeled.

S&P 500 futures fell 0.5 point and 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 rose 4 points, and Nasdaq 100 futures rose 2.75 points.

Strong corporate results have contributed to the market's recent gains, with the S&P up 2 percent since the start of the season. Dow component Chevron Corp is on tap to report later in the morning.

Late Thursday, Dow component Microsoft Corp posted a small dip in quarterly profit, rekindling fears that the popularity of mobile gadgets could erode its main PC-focused business. Still, the stock dipped 0.3 percent to $28.77 before the bell.

Sara Lee Corp said it plans to split into two separate companies. The stock rose nearly 1 percent to $17.80 in premarket trading. Inc's revenues missed expectations late Thursday. Shares of the online retailer fell 7.6 percent to $170.49 in premarket trading.

(Editing by Jeffrey Benkoe)