The report indicates the employment picture is "essentially flat," said Gary Butler, ADP president and chief executive officer.
The private sector market has added an average 37,000 jobs since February, but the downturn, the first in seven months, is another indication the economic recovery has stalled.
On Wall Street, markets found support from foreign equities. Markets in both Asia and Europe made gains Wednesday.
By close, the Dow Jones industrial average added 254.75 points or 2.54 percent to 10,269.47. The Standard & Poor's 500 index added 30.96 or 2.95 percent to 1,080.29. The Nasdaq composite index added 62.81 or 2.97 percent or 2,176.84.
On the New York Stock Exchange, 2,649 stocks advanced and 442 declined on a volume of 4.2 billion shares traded.
The benchmark 10-year Treasury note fell 30/32 to yield 2.57 percent.
The euro rose to $1.2809 from Tuesday's $1.2673. Against the yen, the dollar rose to 84.441 yen from Tuesday's 84.01 yen.
In Tokyo, the Nikkei 225 index added 1.17 percent, 102.96, to 8,927.02.
In London, the FTSE 100 index gained 2.7 percent, 141.19, to 5,366.41.
Copyright 2010 United Press International, Inc. (UPI).