Stock index futures pointed to a lower open on Wall Street on Wednesday, tracking a sell-off in Chinese shares on renewed worries the buoyant market had gone too far ahead of the economic recovery, and as oil prices dipped.

At 3:30 a.m. EDT, futures for the S&P 500 were down 0.81 percent, Dow Jones futures were down 0.8 percent and Nasdaq 100 futures were down 0.91 percent.

The Shanghai Composite Index <.SSEC> fell more than 4 percent on Wednesday as investors were disappointed that authorities did not take steps to support the market after the key index tumbled 20 percent over the past two weeks.

In Tokyo, the Nikkei stock average <.N225> lost 0.8 percent and hit a three-week closing low, falling along with a slide in Chinese stocks that damaged already shaky investor sentiment.

European stocks were down 0.9 percent in morning trade in a broad retreat led by banks such as BNP Paribas and Deutsche Bank .

Tech shares will be in the spotlight on Wednesday on Wall Street after Hewlett-Packard reported slightly better-than-expected quarterly results on Tuesday, helped by strong server sales, but the firm expressed caution about business demand, sending its shares down 2 percent in extended trading on Wall Street. HP shares in Frankfurt were down 0.6 percent.

Oil fell toward $69 on Wednesday, after surging more than 3 percent in the previous session on data that showed a surprise fall in U.S. crude stocks, boosting hopes of a recovery in demand in the world's top energy user.

The day's earnings calendar includes quarterly results from Deere & Co , Limited Brands Inc and Network Appliance , while on the economic data front, the agenda includes MBA Purchase Applications and the U.S. mortgage market index at 7 a.m. EDT.

U.S. shares gained ground on Tuesday, rebounding after sharp losses in the previous session, as stronger-than-expected results from big retailers eclipsed an unexpected drop in housing starts and permits in July.

The Dow Jones industrial average <.DJI> ended up 82.60 points, or 0.9 percent, at 9,217.94. The Standard & Poor's 500 Index <.SPX> closed up 9.94 points, or 1.01 percent, at 989.67. The Nasdaq Composite Index <.IXIC> ended up 25.08 points, or 1.3 percent, at 1,955.92.

The broad S&P 500 index has rallied nearly 50 percent since early March.

(Reporting by Blaise Robinson, editing by Will Waterman)