Simmering tensions between the U.S. and North Korea have come back to the boil in recent days after Pyongyang disclosed plans to fire missiles over Japan to land near America's Pacific territory of Guam.
The Dow Jones Industrial Average slid 33.08 (-0.15 percent) to finish at 22,085.34.
The Standard & Poor's 500 index fell 5.99 points, or 0.2 percent, to 2,474.92.
The Straits Times Index sank 1.31 per cent or 43.52 points to 3,279.72, down 1.4 per cent for the week.
"As a portfolio manager, you say, 'Do I think we'll get a war out of this?' " said Torsten Slok, chief global economist at Deutsche Bank, referring to the bluster between North Korea and President Donald Trump.
Falling crude prices made oil & gas stocks .SXEP a weight too, dropping 1 percent with Tullow Oil the biggest faller.
Vietnam shares fell 2.3 per cent, their most in nine months, dragged down by financials and consumer staples.
Bond prices were little changed. South Korea's KOSPI fell 1.8 percent to almost a three-month low.
Safe havens benefited from the move away from stocks - gold rising again to around $1,290 an ounce after surging 1.3 percent Wednesday - but other risky assets such as oil and copper held their price.
"When you have a market like we have had this year, and it has been amazingly calm, and you introduce a major source of uncertainty, there is bound to be some reaction", said Brad McMillan, chief investment officer for Commonwealth Financial.
London's FTSE 100 closed about 80 points, or more than 1%, lower on Friday, adding to a slump of more than 100 points the day before.
Among company results, Prudential easily beat analysts' profit forecasts at the half-year stage thanks to strong trading in Asia and said it had met its target for surplus cash generation ahead of schedule.
Office Depot tumbled 22.4 percent after the office supplies retailer's quarterly results came in below estimates.
Japan's Topix index had the biggest slide in nearly three months, falling 1.3 per cent on trading volume 22 per cent higher than the 30-day average at the close.
U.S. crude rose 0.41 per cent to US$48.79 per barrel and Brent was last at US$52.01, up 0.21 per cent.
US trading volume has been low with summer setting in and Congress expected to be in recess until September 5.
Benchmark U.S. 10-year notes last rose 6/32 in price to yield 2.1905 percent, from 2.211 percent late on Thursday.
But the safe-haven Japanese yen strengthened 0.33 percent versus the greenback at 110.39 per dollar.
Ongoing global glut concerns lingered in oil markets despite a bigger-than-expected draw in USA crude inventories, leaving prices volatile.