With the second-quarter USA earnings season mostly over, investors are turning their attention from solid economic growth and corporate profits to other risks, said Michael Arone, chief investment strategist at State Street Global Advisors in Boston.
The Russell 2000 index of smaller-company stocks picked up 4.01 points, or 0.2 percent, to 1,690.89.
Rite Aid RAD.N fell 11.5 percent after the drug store chain and US grocer Albertsons Cos ABS.N agreed to terminate their merger agreement.
At 9:48 a.m. EDT the Dow Jones Industrial Average was down 158.88 points, or 0.62 percent, at 25,350.35, the S&P 500 was down 13.35 points, or 0.47 percent, at 2,840.23 and the Nasdaq Composite was down 31.69 points, or 0.40 percent, at 7,860.09.
The S&P financial index fell 1.4 percent, among the biggest drags on the S&P 500.
Tesla shares ended up 0.9 per cent.
Declining issues outnumbered advancing ones on the NYSE by a 2.10-to-1 ratio; on Nasdaq, a 1.51-to-1 ratio favoured decliners.
The tech-heavy index .IXIC was up 0.31 percent at 7,913.03, barely 0.25 percent away from hitting an all-time high.
Oil prices were down slightly as the escalating China-U.S. trade dispute cast doubt on the outlook for crude demand. That compares with the 6.4 billion-share daily average for the past 20 trading days, according to Thomson Reuters data.