Crude oil prices failed to make a decisive recovery on Thursday even though the US sanctions against Iran went into effect on Thursday and the S&P 500 Energy Index closed the day 0.9% lower. The Nasdaq Composite dropped 57.07 points, or 0.72 per cent, to 7,834.71 at the opening bell.
The S&P 500 is up 13.23 points, or 0.5 per cent.
The Russell 2000 index of smaller-company stocks picked up 4.01 points, or 0.2 per cent, to 1,690.89.
The Dow and S&P 500 posted declines for the week following five straight weeks of gains, but the S&P 500 remains just 1.4 per cent below its record high from January 26.
Microchip's shares fell 10.5 percent, the biggest decliner on the S&P, after it forecast disappointing second-quarter revenue.
The Russell 2000 is up 151.29 points, or 9.9 percent.
Second quarter earnings are expected to increase 23.5 percent from the same period a year ago.
At 12:41 p.m. ET, the Dow Jones Industrial Average was down 175.04 points, or 0.69 percent, at 25,334.19, the S&P 500 was down 14.98 points, or 0.52 percent, at 2,838.60 and the Nasdaq Composite was down 27.87 points, or 0.35 percent, at 7,863.91.
Meanwhile, concerns over escalating trade conflict between the US and China weighed on the trade-sensitive S&P 500 Industrials Index, which ended up losing 0.57% on the day.
For the week, the Dow fell 0.6 per cent and the S&P 500 dipped 0.3 per cent.
Russia's dollar-traded RTS index plunged over three percent, Brazil Bovespa index was losing 2.3 percent, and the Turkish Borsa Istanbul index saw a 5.4 percent sell-off.
Tech shares also fell as Facebook, Alphabet and Amazon all declined.
Declining issues outnumbered advancers for a 2.34-to-1 ratio on the NYSE. That compares with the 6.3 billion daily average for the past 20 trading days, according to Thomson Reuters data.