The Shanghai Composite has fallen more than 30 percent from its mid-June peak amid frequent bouts of extreme volatility and analysts say the turbulence is starting to unnerve regional investors.
Commodities were hit on Tuesday on mounting China fears and remained under pressure in Wednesday trade.
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The Federal Open Market Committee (FOMC) minutes will also be in focus, with traders scanning the Federal Reserve's June meeting report for hints on interest rate rise timing.
Greek- and Chinese-related developments should continue to dominate market focus, but the minutes of that FOMC meeting Wednesday should get the market's attention when released at 2 p.m. ET
Meanwhile, the Greek government has until Friday morning to present detailed reform proposals to allow a bailout deal by a Sunday summit.
Greek Prime Minister Alexis Tsipras addressed the European Parliament on Wednesday, lambasting Europe's advocacy of austerity and the efficacy of Greece's bailout programs since 2010, but promised a detailed, "concrete" deal would be presented in the next two to three days.
Other data due for release on Wednesday include consumer credit data at 3 p.m. ET. Major earnings include aluminium producer Alcoa, which is expect to report after market close.
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In Europe,stocks pared losses on Wednesday after Greek Prime Minister Alexis Tsipras said he had submitted reform proposals to creditors.