Wall Street was set for a lower open on Wednesday as continued jitters about Greece's sovereign debt crisis and its potential to spread overshadowed data showing jobs growth in the U.S. private sector.

Private employers in the United States added 32,000 jobs in April, and revisions to previous data showed an unexpected rise in March, according to a report by payrolls processor ADP Employer Services on Wednesday.

Zach Pandl, economist at Nomura Securities International in New York, said the data has taken a back seat to the fiscal crisis in Europe. The market doesn't seem to be paying too much attention to the reasonably good economic news out of the United States today.

S&P 500 futures were down 8 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 fell 65 points, while Nasdaq 100 futures dipped 16.50 points.

Time Warner Inc posted a better-than-expected quarterly profit on a rebound in advertising sales at its cable networks and magazines, but the stock dipped 0.1 percent in premarket trade.

UBS cut its price targets on Alcoa Inc shares and other mining companies. Alcoa dipped 2.1 percent to $12.32 before the bell. Materials and industrial stocks have been under pressure this week as they are sensitive to the outlook of global economic growth.

CONTAGION WARNING

Greek protesters clashed with police as tens of thousands of strikers marched against austerity plans in a crucial test of the government's resolve in enacting deep budget cuts in return for a massive bailout.

Fears over which nation might be next weighed on markets unconvinced that the aid package would stop the crisis from spreading to other vulnerable euro zone countries like Spain and Portugal.

German Chancellor Angela Merkel and the head of the International Monetary Fund warned of financial contagion unless the crisis was halted in Greece.

The problem in the timing of quelling the debt concerns is that there won't be some event that calms people down. It will be a process, as deleveraging takes time, said Peter Boockvar, equity strategist at Miller Tabak + Co in New York.

Oil prices fell to near $80 a barrel, a day after suffering its steepest one-day percentage loss in three months, on rising oil inventories and a firm dollar. The Select Sector SPDR Energy ETF fell 1.1 percent.

Chevron Corp shares were down 1.2 percent at $79.76 and Exxon Mobil Corp dipped 0.7 percent to $66.01.

Global stocks fell to eight-week lows, and the euro hit a one-year trough on Wednesday.

Wall Street had its worst sell-off in three months on Tuesday and the CBOE Volatility Index <.VIX>, Wall Street's so-called fear gauge, finished at its highest level in almost three months.

At 10:00 a.m. EDT, the Institute of Supply Management releases its services sector index for April. Economists expect a reading of 56.0 versus 55.4 in the prior month.

(Additional reporting by Ryan Vlastelica; Editing by Padraic Cassidy)

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