"European shares are trading once again lower. continuing their slide on the back of ever more increasing tensions between North Korea and the United States", added analyst Markus Huber at City of London Markets.
Almost $1 trillion has been wiped out from global equity markets since tensions were sparked off by Trump's "fire and fury" comments on Tuesday.
Gold, another classic safe haven asset, was trading at around $1,291 per ounce, up more than two percent this week and near a nine-week high.
The sabre-rattling - sparked when President Donald Trump stunned the world with an apocalyptic warning to unleash "fire and fury" on North Korea - continued Thursday as Pyongyang mocked the U.S. leader as "bereft of reason".
At 9:38am ET (1338 GMT) the Dow Jones Industrial Average was down 85.43 points, or 0.39%, at 21,963.27, and the S&P 500 was down 10.31 points, or 0.42% at 2,463.71.
"Absent actual military action, I think the markets will realize that the rhetoric got head of the actual policy and it is time to calm down a little bit", McMillan said.
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.
The broad-based S&P 500 shed 0.6 percent to 2,459.50, while the tech-rich Nasdaq Composite Index tumbled 0.8 percent to 6,299.12.
All the 11 major S&P indexed were lower, with technology sector's 0.62% leading the decliners. Shares of J.C. Penney dropped 78 cents, or 17%, to $3.93 Friday after the department store's second-quarter loss exceeded expectations.
On the economic front, figures out on inflation, the Producer Price Index, showed wholesale prices falling for the first time in nearly a year.
The Russian dollar-traded index RTS was down 1.49 percent, and ruble-traded MICEX fell 1.29 percent by midday.
Blue Apron slumped as much as 19.1 percent to a record low after the meal-kit delivery service provider reported a bigger-than-expected loss in its first quarterly report as a public company.
The weaker-than-expected consumer price data in July, which pointed to benign inflation, could cause the Federal Reserve to hold off from raising rates again this year.
Travel operator TUI flew slightly higher after reporting on a strong third quarter performance, with sales and profits taking off during the early summer months, although it left its full year targets unchanged.
Declining issues outnumbered advancers on the NYSE by 2,309 to 518. On the Nasdaq, 1,440 issues fell and 1,386 advanced.