US index futures open slightly negative

Getty Images. These are the stocks posting the largest moves before the bell.

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U.S. stock futures opened Tuesday evening trading slightly negative, implying a roughly flat open based on fair value.

In regular trade, U.S. stocks fell sharply Tuesday on continued signs of weakness in China and concerns about the Federal Reserve .

The major averages ended the day down nearly 3 percent, falling into correction territory. The Dow Jones industrial average (Dow Jones Global Indexes: .DJI) closed about 470 points lower, off session after falling as much as 548 points. The Nasdaq composite (NASDAQ: .IXIC) wiped out gains for 2015, joining the other averages in the red for the year so far.

[Programming note: CNBC will air a special at 7 p.m., ET on the markets]

-CNBC's Gina Francolla and Evelyn Cheng contributed.



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