U.S. stock index futures pointed to a slightly lower open on Thursday as the number of first-time claims for jobless benefits rose unexpectedly, highlighting the bumpy ride for employment as economic growth picks up.

Initial unemployment claims posted their biggest jump in six months, suggesting that despite signs of economic improvement, the labor market still faced headwinds.

In a potentially encouraging sign, however, continuing claims retreated sharply to 3.88 million from 4.13 million.

The number adds fuel to the debate over the real health of the labor market after last week's payroll number, said Andrew Wilkinson, senior market analyst at Interactive Brokers Group in Greenwich, Connecticut. But while this is mildly disappointing, it isn't enough to throw a kink into the idea the global recovery.

Producer prices rose more than expected in December as energy and food costs surged. Underlying inflation remained subdued.

Coming off a broad rally in the previous session, traders looked ahead to Intel Corp's quarterly results, which will be released after the market closes. Intel, a Dow component, is the first major technology company to report earnings and is seen posting revenue growth of 8 percent from the year-ago period.

S&P 500 futures fell 2.6 points and were slightly 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 were down 8 points and Nasdaq 100 futures fell 1.75 points.

Deere & Co rose 1.9 percent to $89.10 in premarket trading after JPMorgan upgraded the stock to overweight on higher North American farmer cash receipts, tax incentives to buy capital equipment and strong crop prices.

Equities have advanced since the start of December in part on hopes that earnings would be strong, though in recent sessions renewed fears over a European sovereign debt crisis partially obscured some strong early results, including from Alcoa Inc .

Spain followed Portugal with a successful debt sale on Thursday, and investors showed growing confidence that governments would agree to new measures to stem the debt crisis.

Williams-Sonoma Inc raised its fourth-quarter outlook after a strong holiday season as margins improved. The shares rose 2 percent to $33.50 in premarket trading.

EXCO Resources Inc rose 2.4 percent to $19.80 before the bell after it said it would explore strategic alternatives, including a buyout proposal from its chief executive.

(Editing by Padraic Cassidy)