U.S. stock index futures dipped into negative territory as after St. Louis Fed President James Bullard said the central bank could taper its $85-billion-a-month bond-buying program during its October meeting.
The dollar rose to a session high against the yen following his comments.
"This was a close decision here in September," Bullard said in an interview with Bloomberg, emphasizing the role that economic data has played and will continue to play in Fed decisions. Bullard is also scheduled to speak on monetary policy to New York Association for Business Economics at 12:55 pm ET.
(Read more: No Fed taper thisyear, says former Bush advisor)
Several other Federal Reserve officials are slated to speak throughout the day. Kansas City Fed President Esther George is due to deliver a speech on the economy to the Shadow Open Market Committee at 12:30 pm ET. Shortly after, Fed Governor Daniel Tarullo speaks at 12:40 pm ET.
And Minneapolis Federal Reserve Bank President Narayana Kocherlakota is expected to talk at a conference on risk in options prices at 1:45 pm ET.
Trading could also be volatile as Friday marks the "quadruple witching," when stock index futures, stock index options, stock options and single stock futures all expire on the same day.
(Read more: Stocks are about toplunge, Wells Fargo pro warns)
Darden Restaurants slumped after the parent company of Olive Garden and Red Lobster posted a much lower-than-expected profit and warned that sales are likely to remain weak at its restaurant chains.
Apple climbed as the tech giant's new iPhone 5C and iPhone 5S went on sale in stores around the world.
In Asia, markets in China, Hong Kong and South Korea were shut for public holidays. Indian stocks led those markets that were open lower, after the Reserve Bank of India unexpectedly raised benchmark rates. Japan's Nikkei index closed just below the flatline and Australia's S&P ASX 200 fell off the previous session's five-year high.
—By CNBC's JeeYeon Park (Follow JeeYeon on Twitter: @JeeYeonParkCNBC)
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FRIDAY: Fed's George speaks, Fed's Bullard speaks, Fed's Kocherlakota speaks
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