Investors kept a wary eye on escalating tensions between the USA and North Korea.
The Dow Jones industrial average lost 50 points, or 0.2%, to 22,032.
The Nasdaq Composite Index plunged 2.1% to 6216.87 and the Standard & Poor's 500 Index dropped 1.45% to 2438.21.
The Nasdaq Composite dropped 49.53 points, or 0.78 per cent, to 6,320.93.
SIMMERING TENSIONS: North Korea revealed on Thursday a detailed plan to launch a salvo of ballistic missiles toward the U.S. Pacific territory of Guam, a major military hub and home to U.S. bombers.
The Swiss franc was on track for its biggest single-day rise against the euro in more than 2 1/2 years.
In more back-and-forth between President Trump and North Korea, Pyongyang General Kim Rak Gyom, leader of the country's strategic forces, said that "sound dialogue is not possible with such a guy bereft of reason and only absolute force can work on [Trump]". That put it at its highest level since the U.S. election in November, as investors piled into safe haven assets such as gold and bonds.
The S&P was only down 0.1 percent for the week entering the session.
The VIX rose further on Wednesday, rising as far as 12.11, its highest in nearly a month. Pyongyang said it was examining plans for attacking Guam, a USA territory in the Pacific with a military base.
Tokyo's blue-chip index tumbled 1.3 percent to its lowest close since late May after the Dow's winning streak of nine straight records ended following Trump's sharp rhetoric of "fire and fury", with the main European bourses also opening lower Wednesday. Hong Kong's Hang Seng was off 0.3 percent. Humana Inc. rose $4.74, or 1.9 percent, to $254.96.
Instead, investors turned to assets that tend to benefit in times of geopolitical and financial stress.
The dollar fell to 109.85 yen from 110.48 yen late Tuesday.
In Europe, Britain's FTSE 100 was down 1.1 percent to 7,306, while France's CAC 40 fell 1.1 percent to 5,058.
The remarks followed a new report asserting that US intelligence has assessed that Pyongyang has successfully produced a nuclear warhead that can fit inside its missiles.
The Russell 2000 is down 39.78 points, or 2.8 percent.
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. Silver also rose, gaining 43 cents, or 2.6 percent, to $16.82 an ounce.
"The market hates uncertainty and that's certainly what we have now", said Ole Hansen, head of commodity strategy at Saxo Bank. I would expect the stock market to react negatively. Core prices had also been expected to climb by 0.2 percent. Brent crude, used to price global oils, gained 56 cents, to $52.70, in London.