About 30 minutes into trading, the Dow Jones Industrial Average was down 0.9 per cent at 18,319.38.
The broader S&P 500 was 1.0 per cent lower at 2,159.50 and the tech-heavy Nasdaq was also 0.9 per cent below yesterday's close at 5,212.21.
In a speech delivered today, Eric Rosengren, president of the Boston Fed and a voting member of the Fed's policy committee this year, suggested a rate hike could be appropriate to avoid an overheating economy.
Apple continued to decline, sinking 0.2 per cent after having lost 2.6 per cent yesterday on disappointing reviews of the new iPhone 7, which fed worries of slowing sales.
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The biotech giant Monsanto was 0.2 per cent higher on word of a possible acquisition by German pharmaceutical company Bayer.
Wells Fargo, which admitted yesterday to opening phony accounts in customers' names and paid USD 185 million in fines, lost 0.3 per cent, running counter to the trend of among other financial stocks, which moved modestly into positive territory.
Before the start of trading, the New York Stock Exchange and Nasdaq observed a moment of silence in memory of those killed in the attacks of September 11, 2001.