U.S. private employers added 238,000 jobs in December, more than expected and the best read since November 2012, while November 2013 numbers were revised higher. The December number was just shy of the highest estimate in a Reuters poll of economists.

"ADP's number is consistent with other labor numbers we have gotten," said Guy Berger, U.S. economist at RBS Securities in Stamford, Connecticut.

"It is conceivable that by the end of year, we could see the unemployment rate to fall below 6.5 percent," he said. "That would be consistent with the (Federal Reserve's) projected pace of tapering this year."

Minutes of the Fed's December meeting, at which the U.S. central bank announced its decision to begin trimming its stimulative monthly bond purchases, are out later on Wednesday. Market participants will scan the minutes for signs of a clear Fed commitment to keeping rates low for a long time.

S&P 500 futures fell less than a point and were little changed in terms of 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 fell 11 points and Nasdaq 100 futures were up 3 points.

Micron Technology (MU.O) shares jumped 9.8 percent in premarket trading a day after it reported a much higher-than-expected quarterly profit.

Microsoft (MSFT.O) is closer to naming a new chief executive, according to a source familiar with the board's thinking, but it lost a front-runner candidate Tuesday when Ford's (F.N) chief, Alan Mulally, said he would not be going to the software giant. Microsoft shares edged 0.7 percent lower in trading before the opening bell.

A deadly blast of arctic air shattered decades-old temperature records as it enveloped the eastern United States on Tuesday, snarling air, road and rail travel, driving energy prices higher and overwhelming shelters for homeless people. Economic activity is also expected to be hurt beyond airlines and other transport companies.

"Coming off the Christmas season you have a lot of sales but the weather hasn't collaborated," said Andre Bakhos, managing director at Janlyn Capital in Bernardsville, New Jersey.

The pharma sector continued to be fertile for merger and acquisition activity. Forest Laboratories (FRX.N) agreed to buy privately held specialty pharmaceutical company Aptalis Holdings Inc for about $2.9 billion. Forest Labs shares rose 10.5 percent in premarket trading.

NuPathe Inc (PATH.O) shares jumped 33 percent in premarket trading after it said it received a buyout offer from Israel's Teva Pharmaceutical (TEVA.TA) for $114 million plus milestone payments related to a migraine treatment.