Volatility gauges from the USA to Japan rose after president Donald Trump said in response to a Washington Post report on North Korea's nuclear capabilities that further threats from the country would be met with "fire and fury".
Small-company stocks fell more than the rest of the market Wednesday.
ASIA'S DAY: Earlier, Asia bore the brunt of the mounting geopolitical uncertainty, with South Korea's Kospi index closing down 1.7 percent at 2,319.71 and Hong Kong's Hang Seng ending 2 percent lower at 26,883.51.
S&P 500 e-minis were up 1.5 points, or 0.06 percent, with 300,073 contracts traded.
The Nasdaq composite slumped 135.46 points, or 2.1 percent, to 6,216.87. While the German DAX Index has edged down by 0.1 percent, the French CAC 40 Index and the U.K.'s FTSE 100 Index are both down by 1 percent.
TIME OUT: Fossil tumbled 23.6 percent after the watch maker said sales continued to weaken, falling short of analysts' estimates.
BAD TRIPS: Priceline Group slid 8.2 percent after the online travel booking service issued a profit forecast that was weaker than analysts were expecting.
On average, the S&P 500 falls 5% or more every 10 weeks and the index falls 10% every 33 weeks, according to data analyzed by AllianceBernstein going back to 1928.
Significant strength was also visible among software stocks, as reflected by the 1.2% gain posted by the Dow Jones Software Index. The major index futures are now pointing to a modestly higher open for the markets, with the Dow futures up by 21 points.
Canada's main stock index fell to its lowest close in a month on Thursday as oil prices fell and investors sought refuge in safe-haven assets amid rising tensions between the United States and North Korea.
Disney dropped 4.5 percent after reporting a weak quarter and saying it would pull its movies from Netflix and start two of its own video streaming services. Consumer-focused companies and banks were among the biggest decliners. TripAdvisor shares shed $2.70, or 6.8 percent, to $36.85. The company booked a hefty charge and said its CFO is leaving.
In other energy futures trading, wholesale gasoline was little changed at $1.62 a gallon, heating oil rose 2 cents, to $1.65 a gallon, and natural gas rose 6 cents, to $2.88 per 1,000 cubic feet.
The Canadian dollar was trading at an average price of 78.67 cents USA, down 0.04 of a U.S. cent. Brent crude, used to price global oils, gained 56 cents, to $52.70, in London. The yield on the 10-year Treasury note fell to 2.22 percent from 2.26 percent late Tuesday. The euro held steady at $1.1752. Copper fell 2 cents, to $2.93 a pound. Humana Inc. rose $4.74, or 1.9 percent, to $254.96.