U.S. President Donald Trump on Thursday warned Pyongyang again, saying his previous promise to unleash "fire and fury" may not have been strong enough after North Korea responded with a threat to fire missiles over Japan to land near the U.S. Pacific territory of Guam.
The Nasdaq Composite was down 37.30 points, or 0.59 percent, at 6,315.03.
UN Secretary-General Antonio Guterres said he was deeply concerned about the tensions on the Korean Peninsula and was "troubled" by the increase in confrontational rhetoric.
The Dow industrials rose 14.31 points, or less than 0.1%, to 21858.32 on Friday.
The data comes amid tepid inflation that has remained below the Fed's 2% target, despite low unemployment.
"I will tell you this, North Korea better get their act together or they're going to be in trouble like few nations ever have been in trouble in this world", Trump said. Discovery Communications declined 2.9%, while Viacom shed 1.9%.
Technology companies led a broad slide in USA stocks Thursday afternoon, putting the market on track for its biggest loss in two months.
Meanwhile, the Russell 2000 index of small-cap stocks looked poised for a weekly drop of almost 3%, its biggest one-week decline since February 2016.
The CBOE Volatility Index - a measure of investors' expectations for swings in the S&P 500 over the next 30 days - surged Thursday to its highest level since U.S. Election Day.More news: Facts About North Korean Dictator Kim Jong Un
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On the economic front, figures out on inflation, the Producer Price Index, showed wholesale prices falling for the first time in nearly a year.
Outside the political arena, declines in a pair of technology stocks added to the cautious tone on the day. Shares of Macy's lost 10% and Kohl's fell 5.8%.
Options traders gear up for Snap's second earnings report as a public company. The stock has more than doubled over the past 12 months, gaining more than 160%. It has been more than a year since the last 5% downdraft in stocks and more than 76 weeks since the stock market suffered a 10% loss.
If the North Korean regime "does anything" to the USA or a United States ally "things will happen to them like they never thought possible", he told reporters on Thursday, according to Bloomberg.
Stock movers:Nordstrom Inc.(JWN) shares earlier rose after the retailer posted earnings that beat expectations (http://www.marketwatch.com/story/nordstrom-shares-rise-after-retailer-tops-views-sales-rise-2017-08-10) but the stock is trading mostly flat.
RETAIL SLUMP: Disappointing quarterly results from big department store chains put investors in a selling mood.
Uncertainty over North Korea also reverberated in the foreign exchange market, where safe-haven currencies such as the Japanese yen and Swiss franc rallied.
Among other markets, oil prices advanced after a US Department of Energy report showed lower oil inventories.