U.S. stock index futures pointed to a sharply lower open on Thursday as a report that regulators were intensifying their review of European banks' U.S. units shook up investors.

Concerned the European debt crisis might spread to the U.S. banking sector, the Federal Reserve Bank of New York has asked for more information about whether the banks have reliable access to funds needed to operate, the Wall Street Journal reported. For details, see [ID:nL5E7JI0Q]

Investors continued to worry that European policymakers were not doing enough to tackle the euro zone's debt crisis. European blue chips were down 3.1 percent, with banks among the biggest losers.

The select sector SPDR financial ETF, an exchange-traded fund made up of U.S. bank stocks, dropped 2.8 percent.

The slide in futures is rooted in the European banking system, said Jack de Gan, chief investment officer at Harbor Advisory Corp in Portsmouth, New Hampshire.

It reflects continued concern that sovereign debt issues indicate we're going to have to bail out all those banks again. And if there's stress in major European banks, it will affect U.S. banks too.

S&P 500 futures fell 27.2 points and were sharply below fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration of the contract. Dow Jones industrial average futures tumbled 228 points, and Nasdaq 100 futures dropped 48 points.

Futures ticked even lower after separate U.S. government reports showed new jobless claims rose more than expected last week, while consumer prices rose faster than expected in July. [ID:nOAT004857] and [ID:nOAT004856]

Data on leading indicators and home resales as well as the Philadelphia Fed's business activity index are due at 10 a.m.

EDT. (1400 GMT)

Concern about the global economy was underscored by a Morgan Stanley note on Wednesday that cut its 2011 and 2012 global gross domestic product forecasts. [ID:nL3E7JI1LM]

Shares of NetApp Inc fell 14 percent to $35.84 in premarket trading a day after the data storage equipment maker forecast a weak second quarter in a further indication of soft tech spending by governments and large companies.

(Reporting by Rodrigo Campos; editing by Jeffrey Benkoe)