U.S. stock-index futures indicated a sharply lower open on Thursday, tracking European shares, after soft data from Italy and as investors worried about one of Portugal's top banks.
Stock futures remained steeply under water, offering no reaction to U.S. economic data after the government reported 304,000 claims for jobless benefits were filed last week, down 11,000 and better than expected.
Read MoreUS jobless claims flirt with 300K, eye post-recession lows
"Portugal's bank still has a problem, no matter what jobless claims were. We used to have a Europe crisis every two weeks, now we have one every nine months," said JJ Kinahan, chief strategist at TD Ameritrade.
In Europe, stocks from the euro zone's periphery led declines. Portugal's PSI 20 Index fell by around 3 percent amid concerns about the health of the financial group Banco Espirito Santo.
It comes after U.S. stocks climbed on Wednesday - following two days of falls - as traders digested minutes from the Federal Open Market Committee which noted an improving economy and labor market. They also revealed that the central bank planned to end its quantitative easing program by October, and that - while it had no date to raise rates - it had been working on details of a plan to return to normalcy.
Barclays analysts said the market had positioned for a more hawkish tone to the minutes.
"In recent days, shorter-dated U.S. yields have been creeping higher and equity markets have been subdued, as stronger data brought forward expectations for Fed tightening," the analysts said in a morning note.
Read MoreDovish Fed pushes back on rate hike speculation
"However, the minutes struck a more balanced tone on the inflation outlook and advocated the use of macro-prudential measures rather than rate hikes to address financial stability issues."
But analysts were cautious as second-quarter earnings season gets underway. It kicked off with Alcoa earlier this week, although the aluminium producer's quarterly profit beat expectations.
"Earnings season will go a long way towards showing us that we don't have growth," Todd Horwitz, author and founder of Averagejoeoptions.com, told CNBC on Thursday.
Read MoreFed minutes: QE likely to end with $15 billion in October
Wholesale inventories data are due to be published at 10 a.m. ET, with consensus forecasts calling for a 0.5 percent increase in inventories after a 1.1 percent increase in April.
Kansas City Fed President Esther George and Dallas Fed President Richard Fisher are also due to speak.