US STOCKS-Futures flat as GDP, jobless data awaited

* Economy seen rising at 2.1 pct rate in revised GDP

* Einhorn calls for Microsoft CEO to depart

* Tiffany rallies on results, outlook before open

* Futures: Dow up 19 pts, S&P up 2 pts, Nasdaq flat

* For up-to-the-minute market news see [STXNEWS/US] (Adds analyst comment, updates prices)

By Ryan Vlastelica

NEW YORK, May 26 (Reuters) - U.S. stock index futures were little changed on Thursday as investors looked ahead to data that could shed light on the economy's health amid worries that global demand was slowing.

Equities have been pressured recently, with the S&P 500 down 3.2 percent so far this month. Investors said Wednesday's rally, which broke a three-day losing streak, may not be enough to overcome macroeconomic worries.

In a sign of rising concerns about the economic outlook, Goldman Sachs lowered its year-end target for the S&P to 1,450 from 1,500, citing margin concerns. For details, see [ID:nL3E7GQ1OM]

The preliminary estimate of first-quarter gross domestic product is due at 8:30 a.m. (1230 GMT) and is seen rising by 2.1 percent compared with the 1.8 percent rate previously estimated by the government.

Though the economy was seen expanding in the quarter despite sovereign debt woes, geopolitical tensions and natural disasters overseas, a weaker-than-expected reading could exacerbate concerns about global growth.

"The GDP number will give us some insight into how the second quarter is going so far. So if it disappoints, you could see (the S&P) fall by as much as 1.5 percent," said Peter Cardillo, chief market economist at Avalon Partners in New York.

Cardillo noted that the number would reflect the impact from Japan's earthquake, which could be a drag on first-quarter U.S. GDP but could provide a boost for growth in future quarters. "The economy is going through a soft patch now, but I think yesterday's movement to the upside will probably carry forward," he said.

Weekly jobless claims are also on tap, with 400,000 initial claims expected, down from the 409,000 posted last week but still considered high.

S&P 500 futures rose 2 points and were even with 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 added 19 points and Nasdaq 100 futures were flat.

Hedge fund manager David Einhorn called for Steve Ballmer, the chief executive of Microsoft Corp , to step down. Shares of the Dow component rose 0.9 percent to $24.41 in premarket trading. [ID:nN25183623]

Tiffany & Co shares rose 2.3 percent to $71.65 in premarket trading after the luxury retailer reported its first-quarter results and raised its outlook. [ID:nN26228628]

Sony Corp's <6758.T> forecast of its first annual net profit in four years was viewed as optimistic, as the consumer electronics giant struggles with the aftermath of the March earthquake and a series of network security breaches. [ID:nL3E7GQ0UW]

The Federal Reserve Bank of New York is investigating whether Goldman Sachs' mortgage servicing arm did not conduct proper reviews before denying borrowers the option to lower their payments under a government loan modification program. [ID:nN25185994] (Editing by Kenneth Barry)