* ADP private labor market cuts worse than expected
* Futures: Dow down 21 pts, S&P down 3.1, Nasdaq off 4.75
(Updates with ADP jobs data)
By Edward Krudy
NEW YORK, Sept 2 (Reuters) - U.S. stock index futures pointed to lower open on Wall Street on Wednesday after a private jobs report added to investor concerns over the direction of the economy and indicated more losses after a three-day slump.
U.S. private employers cut 298,000 jobs in August, fewer than a revised 360,000 jobs lost in July, but more than the 250,000 mean forecast in a Reuters poll, the ADP and Macroeconomic Advisers said its National Employment Report.
The report is seen as a precursor to closely-watched monthly government figures on employment on Friday, with investors looking for any evidence that the S&P 500's 50-percent rally since early March may have run too far ahead of the economy.
"Well it's not a lot of reaction but not actually a good number," said Frank Lesh, futures analyst and broker at Futurepath Trading in Chicago. "I don't know that we're going to react a whole lot to that. We've already had a pretty good sell-off."
S&P 500 futures fell 2.9 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 were down 21 points, and Nasdaq 100 futures dropped 4.5 points.
A separate report from Challenger, released earlier on Wednesday, showed planned layoffs by U.S. firms fell 21 percent in August.
Other data Wednesday includes U.S. Commerce Department figures for July factory orders, due at 10 a.m. Economists in a Reuters survey expect an increase of 2.2 percent compared with a 0.4 percent rise in June.
Later, the Federal Reserve releases its Federal Open Market Committee meeting minutes at 2 p.m., which are closely followed for an insight into the Fed's thinking on the economy.