Six of the 11 major S&P sectors were higher, with the technology's 0.36 percent rise leading the advancers.
Cracks are showing in what has been a virtually non-stop US equity rally after a rapid escalation of tension between North Korea and the United States this week.
About 15 minutes into trading, the Dow Jones Industrial Average had dropped to 21,947.15, down 0.5 percent from Wednesday's close, falling back below the 22,000 mark it first broke through on August 2. The Dow slumped 204.69 points or 0.9% to 21,844.01, the Nasdaq plummeted 135.46 points or 2.1% to 6,216.87 and the S&P 500 tumbled 35.81 points or 1.5% to 2,438.21.
Global markets have been on edge since Tuesday, when President Donald Trump warned North Korea of severe retribution should the authoritarian state proceed with any more missile tests or threats.
The tensions, since Trump's "fire and fury" comments on Tuesday, have wiped out almost $1 trillion from the global equity markets.
"The typical text book trade is that investors rush for safe havens". The S&P shed 1.4%, its worst week since March, while the Nasdaq posted a weekly loss of 1.5%, its worst since June.
The VIX rose further on Wednesday, rising as far as 12.11, its highest in nearly a month.
However, an Associated Press report that the USA and North Korea have been engaged in back channel talks (https://apnews.com/686ac7c761694b28b67793a1d8297145?link=mktw) for several months even as they exchange incendiary threats helped to soothe some of the jitters.
Inter, Kondogbia non si presenta. Spalletti: "Vuole andare via"
Con gli addii di Medel e Murillo l'Inter deficita numericamente in difesa: "In questo momento abbiamo la coperta cortissima". Il centrocampista vuole andarsene e l'Inter lo vorrebbe vendere, ma non in saldo.
France's CAC dropped 1.6 per cent and Germany's DAX fell 1.3 per cent. Macy's sank 10.3 per cent and Kohl's lost 5.8 per cent.
The local currency closed at 1,143.50 won against the USA dollar, down 1.50 won from the previous session's close.
MSCI's main index of Asia-Pacific shares, excluding Japan, was last down 0.6 percent.
Instead, investors turned to assets that tend to benefit in times of geopolitical and financial stress. Japan is the world's biggest creditor country and there is an assumption investors there will repatriate funds in a crisis. Banks and department store shares also were among the big decliners.
Biotech company Novozymes gained 1.16 percent in Copenhagen after cutting its growth outlook.
"Heightened geopolitical risks overnight have seen the markets flip from risk-on to risk-off and we have to wait and see how long this move runs before adding some positions", said Viraj Patel, an FX strategist at ING in London.
"We're not very oversold yet so the market still has more downside left to it", said Robert Pavlik, chief market strategist at Boston Private Wealth in NY. Against the euro, the dollar is valued at USD1.826 compared to yesterday's USD1.1772.