Stock index futures point to mixed open

Automatic Data Processing (ADP) releases its April employment report at 8:15 a.m. EST. Economists in a Reuters survey expect 30,000 jobs were created in April versus a loss of 23,000 jobs in March.

At 7 a.m. EST, Mortgage Bankers Association releases Weekly Mortgage Market Index for the week ended April 30, versus the prior week. The mortgage market index read 534.5 and the refinancing index was 2,161.8 in the previous week.

Major companies announcing results included Time Warner, Intercontinental Exchange, Prudential Financial and CBS Corp.

Oil fell toward $82 a barrel, extending the steepest one-day percentage loss in three months in the previous session, on rising oil inventories and a firm dollar.

Investors dumped U.S. stocks on Tuesday in Wall Street's worst session in three months on the fear that even with a bailout for Greece, Europe's debt crisis could spread to other weak euro zone countries.

Teams of oil spill workers were set to take to advantage of at least one more day of calm in the Gulf of Mexico on Wednesday to keep fighting to contain a huge and growing slick before winds turn against them.

The Dow Jones industrial average lost 225.06 points, or 2.02 percent, to 10,926.77. The Standard & Poor's 500 Index fell 28.66 points, or 2.38 percent, to 1,173.60. The Nasdaq Composite Index dropped 74.49 points, or 2.98 percent, to 2,424.25.

Greece is likely to grind to a halt on Wednesday as protests intensify against draconian measures to secure financial aid, sending global stocks and the euro tumbling and stoking anxiety about an EU debt contagion.

"Who's next" was the question weighing on markets unconvinced that a record 110 billion euro ($142.8 billion) EU/IMF bailout for Greece would stop its economic woes spreading to other vulnerable euro zone countries, such as Spain and Portugal.

European credit derivatives indexes widened, extending Tuesday's slump.

A multi-billion euro international aid plan for Greece will determine the future of Europe and Germany's role within it, German Chancellor Angela Merkel said on Wednesday.

Greece's debt woes give China reason to proceed cautiously with currency reform but, barring a crisis that shakes Europe, should not stand in the way of a resumption of appreciation, government advisers said on Wednesday.

Challenger, Gray & Christmas Inc. releases at 7:30 a.m. EST its report on job cuts for April. Challenger reported 67,611 layoffs in the prior month.

At 10 a.m. EST, Institute for Supply Management releases its April non-manufacturing index. Economists in a Reuters survey forecast a reading of 56.0 versus 55.4 in March.

Airspace over Scotland and Northern Ireland will be closed from early Wednesday because of volcanic ash that closed airports in Ireland on Tuesday and could threaten summer holiday travel.

Shares of News Corp reversed course to fall more than 4 percent in extended trade on Tuesday after the company reported quarterly results.

European shares fell on Wednesday after sharp falls in the previous session, with banks the major losers, but forecast beating results from Societe Generale and commodity stocks provided some support. The pan-European FTSEurofirst 300 index of top shares was down 0.8 percent.

(Reporting by Atul Prakash; Editing by Hans Peters)