Nasdaq 100 e-minis were down 40.25 points, or 0.68 percent, on volume of 29,918 contracts.
Gains among technology companies helped snap a three-day losing streak for US stocks Friday, though the market ended with its worst weekly loss since March.
Commenting on the situation in markets, David Madden, senior market analyst at CMC Markets UK said: "The tension between the USA and North Korea is still dominating the news and it is looming over the financial markets".
"While the U.S. President insists on ramping up the war of words, there is a decreasing chance of any diplomatic solution", Carnell said.
US Defence Secretary Jim Mattis, who often has emphasised the devastating costs of any conflict with North Korea, seemed to back up Trump's tone.
Some investors are on edge after U.S. President Donald Trump warned North Korea of "fire and fury".
"While the two nations are at loggerheads, it is going to be hard to imagine money flowing into stocks", said David Madden, market analyst at CMC Markets UK.
'Traders are on red alert as the mention of war has sent them running for cover. "Whether it is a credit crunch in China, policy error from the Fed, or fear of an over-valued US stock market, there are many reasons to maintain a balanced multi-asset portfolio that has exposure to defensive asset classes and currencies".
Crystal Palace 0-3 Huddersfield Town
Crystal Palace manager Frank de Boer says that getting his new club into mid-table will feel like winning the title with Ajax. Crystal Palace , on the other hand, has made some good signings and will look to further build from last season.
Tottenham boss Pochettino insists he will sign players
"Obviously, we had some games that were not the best but I think there were games where we played really good", Dembele said . Victor Wanayama is also set to miss the trip due to a knee injury sustained whilst away on Spurs' pre-season tour of the US.
Premier League Live is back on Today FM
Chelsea striker Alvaro Morata has said that he's ready to prove doubters wrong and feels motivated for the Premier League to start.
Earlier, Pyongyang said it was ready to give Washington a "severe lesson" with its strategic nuclear force in response to any US military action.
The Dow Jones industrial average fell 36 points, or 0.2 percent, to 22,048. Regions Financial shed 23 cents, or 1.6 percent, to $14.07. Hong Kong's Hang Seng added 0.6 percent.
South Korea's won currency dropped 0.9 percent against the dollar to its lowest close since July 13. A weakness in the consumer discretionary, financials, and information technology sectors weighed on the market.
Raytheon, which manufactures Tomahawk cruise missiles jumped +2.57% while other defense contractors such as Lockheed Martin (+1.71%), Northrop Grumman (+1.22%) and L3 Tech (+1.99%) also saw gains.
Spot gold inched down 0.1% to $1,284.64 per ounce as of 11.46am, but was set for a weekly gain of over 2%. The precious metal miners benefited from the flight to safety, with bullion prices hitting near two-month highs on North Korean worries.
Markets are now awaiting USA consumer price data for July, due later in the session.
Orders fell 4.7 percent from the previous quarter in April-June, suggesting demand is weaker than expected, though economists say the outlook for coming months is more upbeat.
The department store chain reported earnings of $110 million, or 65 cents a share.
USA crude oil futures settled almost 2 per cent lower at $48.59 a barrel, as Russian Federation considered a future output resumption and the Organization of the Petroleum Exporting Countries boosted its July production numbers.