Stock index futures pointed to a lower opening on Wall Street on Wednesday, with futures for the S&P 500 and Dow Jones down around 0.1 percent, while the Nasdaq 100 fell 0.4 percent at 4:10 a.m. EDT.

The expected weakness on Wall Street chimes with fresh 2012 lows in Europe, where the FTSEurofirst 300 traded down 0.9 percent, and in Asia as investors fret about Greece.

Greek political leaders will attempt on Wednesday to form a caretaker government to take the country to a second election in just over a month, with its euro membership at stake and its president speaking of fear that could develop into panic at its banks.

Global mining shares have been hit after BHP Billiton said it expects commodity markets to cool further and that investors have lost confidence in the longer-term health of the global economy.

Wednesday's data diary features housing starts and building permits for April at 1230 GMT, followed by industrial production figures at 1315 GMT, with both expected to show an improvement from the previous month.

The minutes from the Federal Reserve's April meeting, due at 1800 GMT, will be scrutinized for any discussion on the health of the labor market as investors debate the likelihood of more stimulus measures.

A fairly thin earnings calendar includes first quarter figures from the farm equipment maker Deere , Victoria's Secret parent Limited Brands Inc., office supply chain Staples and retail giant Target .

The retailers will be in the spotlight after J.C. Penney posted a steeper-than-expected drop in first quarter sales late on Tuesday, sending its shares down nearly 13 percent after the bell.

U.S. stocks fell for the eighth day in the past 10 on Tuesday. The Dow Jones industrial average dropped 63.35 points, or 0.50 percent, to close at 12,632.00. The Standard & Poor's 500 Index lost 7.69 points, or 0.57 percent, to 1,330.66. The Nasdaq Composite Index fell 8.82 points, or 0.30 percent, to close at 2,893.76.

Facebook Inc. will increase the size of its initial public offering by 25 percent, a source familiar with the matter said, and could raise as much as $16 billion as strong investor demand for a share of the No.1 social network trumps debate about the company's long-term potential to make money.

The news comes as General Motors Co plans to stop advertising on Facebook, with a source familiar with the matter saying the automaker had decided the ads had little impact on consumers.

General Electric Co. is buying two mining equipment firms, Australia's Industrea Ltd for $700 million as well as a privately held U.S. company, as it seeks to boost its presence in a $61 billion industry.

NYSE Euronext is out of the race to buy the London Metal Exchange, after its reported 800 million pound ($1.28 billion) bid was deemed too low.

The FBI has opened an inquiry into the multibillion-dollar trading losses at JPMorgan Chase , stepping up pressure on the bank after key U.S. agencies said they were looking into high-risk trades that first drew regulators' attention last month.

(Reporting by Toni Vorobyova; Editing by Catherine Evans)