U.S. stock index futures dipped on Wednesday after four straight days of gains for the benchmark S&P 500 as investors awaited data on the labor market and manufacturing.

ADP employment data, due at 8:15 a.m. EDT, is expected to show U.S. private employers added 175,000 jobs in May, according to a Thomson Reuters poll of analysts, down slightly from 179,000 in April. The report comes ahead of the closely watched non-farm payrolls data Friday and after a batch of recent indicators suggested slowing growth.

Data Tuesday showing a drop in business activity in the U.S. Midwest added to other regional reports that have pointed to slower growth in manufacturing this month amid supply chain disruptions from the March earthquake and tsunami in Japan.

That bodes poorly for the Institute for Supply Management's manufacturing report, which is expected to slow, and casts a cloud ahead of a report on national employment on Friday.

The ISM monthly factory indicator, due at 10 a.m. EDT (1400 GMT), is seen easing to 57.7 from the prior month's 60.4.

Construction spending for April is expected to show a rise of 0.3 percent after March's increase of 1.4 percent. The data is also due at 10 a.m. EDT. (1400 GMT)

After four up days, culminating in a month-ending, window dressing session, we have nearly reversed the down trend move. With no fresh themes to drive the market, investors may be wary to put fresh money to work, said Andre Bakhos, director of market analytics at Lek Securities in New York.

This coupled with the recent bevy of less than impressive economic numbers and we have the recipe for an overall market hesitation.

S&P 500 futures shed 0.6 points and were slightly below 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 lost 23 points, and Nasdaq 100 futures fell 2 points.

Yahoo Inc shares dipped almost 1 percent to $16.41 in premarket trading after two sources said it resolved a dispute with partner Alibaba Group over the Chinese company's transfer of its prized online payments unit to Chief Executive Jack Ma.

Sprint Nextel Corp asked U.S. regulators to block AT&T Inc's proposed $39 billion purchase of T-Mobile USA, saying the deal has no public interest benefit and would harm competition.

European stocks were little changed early Wednesday, halting a week-long recovery rally as investors awaited U.S. jobs data, looking for more insight on the world's biggest economy. <.EU>

Wall Street bulls took the upper hand with a 1 percent rally on Tuesday as hopes for a new bailout for Greece relieved some investor worry, but grim economic data suggested more hurdles ahead as the S&P 500 closed out its worst month since August.

(Reporting by Chuck Mikolajczak; editing by Jeffrey Benkoe)