Pre-market data

US index futures slightly negative and pointing to flat open based on fair value

Traders work on the floor of the New York Stock Exchange.
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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 closed about 470 points lower, off session after falling as much as 548 points. The Nasdaq composite 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.