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 (1215 GMT), 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.

The Institute for Supply Management's monthly factory indicator, due at 10 a.m. EDT (1400 GMT), is seen easing to 57.7 from the prior month's 60.4. Supply chain disruptions after the Japanese earthquake and tsunami are being blamed for pushing the index lower this month.

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)

S&P 500 futures shed 1.2 points and were 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 5.25 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 steady 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)