The Dow is down 98.98 points or 0.5% at 21,949.72, the Nasdaq is down 65.83 points or 1% at 6,286.50 and the S&P 500 is down 16.77 points or 0.7% at 2,457.25. "What's happened in North Korea is enough to do that".
Simmering tensions between the United States and North Korea have come back to the boil in recent days after Pyongyang disclosed plans to fire missiles over Japan to land near America's Pacific territory of Guam.
Valeant's stock, which rallied a day before following quarterly results, sank 9.6 percent to C$17.85 after it said its subsidiaries in Australia were the subject of a tax audit. The Russell 2000 index of smaller-company stocks gave up 4.02 points, or 0.3 percent, to 1,410.15.
In the cash market, the blue chip Dow Jones industrial Average is trading 22028.67, down 56.67 or -0.26%.
Six of the 11 major S&P sectors were higher, with the technology's 0.36 percent rise leading the advancers. President Donald Trump said on Tuesday that US threats from Pyongyang would be met with "fire and fury", which prompted North Korea to say it was considering plans for a missile strike on the USA pacific territory of Guam.
Small-company stocks fell more than the rest of the market Wednesday.
The selling was also in response to lower prices in Asia and Europe. Non-OPEC production will get a health check later today when the Baker Hughes U.S. rig count is published at 1:00 p.m.
The market indexes wavered between small gains and losses for much of the morning, then veered lower by afternoon. It was the biggest percentage loss since mid-June.
The CBOE Volatility Index, better known as the VIX and the most widely-followed barometer of expected near-term stock market volatility, closed at 10.96, its highest in about a month.
Nasdaq 100 e-minis were down 1 points, or 0.02 percent, on volume of 49,062 contracts.
Shares of Kohl's Corporation surged 7% in premarket trading Thursday before giving up those gains, after the retailer reported earnings that beat Wall Street estimates. Companies in the S&P 500 are set to report stronger second-quarter earnings than analysts expected, according to FactSet, lifted by oil-and-gas companies benefiting from stabilizing oil prices and multinational firms profiting from a weaker dollar.
Data showed US producer prices unexpectedly fell in July, recording their biggest drop in almost a year, while another set showed the number of Americans filing for unemployment benefits unexpectedly rose last week.
S&P 500 e-minis were up 1.5 points, or 0.06 percent, with 300,073 contracts traded.