Stock index futures fell on Thursday, following global stocks lower, as persistent fears over Greece's public finances unsettled investors worried about sovereign debt defaults in Europe.

Markets pounded Greek bonds and banking stocks, driving the country's borrowing costs to new highs and pushing it closer to tapping a last-resort safety net.

Greece is the word that just seems never to go away, said Kim Caughey, senior equity research analyst at Fort Pitt Capital Group in Pittsburgh. What is the EU going to do, and structurally how are they going to address this? I think that's the big question because we have Spain, Portugal looming out there as well.

S&P 500 futures fell 4.9 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 dropped 33 points, and Nasdaq 100 futures lost 5.5 points.

Data on weekly initial claims for jobless benefits is due before the bell, an important indicator on the state of the economy as optimism grows about the strength of the labor market. Economists in a Reuters poll expect that new claims fell by 4,000 last week.

U.S. retailers hope an early Easter holiday helped draw more shoppers into stores in March. Top store chains, including Target Corp and Macy's Inc , are due to report monthly sales, offering a snapshot into the health of the U.S. consumer.

Shares of UAL Corp , parent of United Airlines, jumped 8.9 percent to $20.64 in premarket trade after the New York Times reported the company was in merger talks with US Airways Group Inc , citing sources.

Apple Inc will show off the newest operating system software for its iPhone Thursday, as the company prepares for the launch of its next generation smartphone later this year.

With U.S. Treasury Secretary Timothy Geithner on a quick trip to Beijing, the New York Times reported China is very close to announcing a shift in its currency policy. Geithner is expected to urged China to permit a renewed rise in the currency.

The pan-European FTSEurofirst 300 <.FTEU3> index of top shares fell 1.2 percent, while the euro inched closer to a 2010 low against the dollar on jitters over Greece.

U.S. equities pull backed Wednesday after hitting levels not seen in a year and half. The Dow industrials fell back from the psychologically important 11,000 level. (Reporting by Edward Krudy; editing by Jeffrey Benkoe)