European stocks dipped early on and Japan's Nikkei .N225 average fell to a three-week closing low as uncertainty surrounding a potential bailout for debt-stricken Spain and further signs of a slowdown in China rattled investors.

China's official purchasing managers' index for the services sector fell in September, showing the world's second-largest economy looks set for a seventh straight quarter of slowdown.

Automatic Data Processing releases its September employment report at 8.15 a.m. EDT. Economists in a Reuters survey expect 143,000 jobs were created in September versus 201,000 in August.

The Institute for Supply Management publishes its September non-manufacturing index at 10 a.m. EDT. A reading of 53.2 is expected, versus 53.7 in August.

Best Buy Co Inc (BBY.N) founder Richard Schulze and at least four private equity firms have started examining the books of the world's largest consumer electronics chain, early steps toward what could become a potential $11 billion buyout, according to people familiar with the matter.

Google (GOOG.O) subsidiary Motorola Mobility has dropped a complaint of patent infringement against Apple (AAPL.O) without explanation.

Hewlett-Packard's (HPQ.N) holds an analyst day meeting and investors may grill Chief Executive Meg Whitman on how she plans to reverse a share price that has lost more value this year than almost any other major technology company. Wall Street is keeping one eye on the printing division, which Whitman's predecessor once considered spinning off.

Monsanto, the world's largest seed company, is expected to post a loss per share of $0.43 for its fourth quarter, compared to $0.22 one year earlier. The period is traditionally Monsanto's weakest because of the seasonality of sales of its key seed products.

Marriott International, the second-largest U.S. hotelier, and retailer Family Dollar are also due to report quarterlies.

The Standard & Poor's 500 Index .SPX closed up 1.26 points, or 0.09 percent, at 1,445.75 on Tuesday. The Dow Jones industrial average .DJI was down 32.83 points, or 0.24 percent, at 13,482.28. The Nasdaq Composite Index .IXIC was up 6.51 points, or 0.21 percent, at 3,120.04.

(Reporting By Francesco Canepa; editing by Stephen Nisbet)

• A Permanent Economic Emergency