"There is low volatility in the markets as the S&P and Nasdaq are just below all-time record highs, and it seems like markets are complacent right now", said Tom White, chief market strategist at TradeWise Advisors, in Chicago, Illinois. "You worry about the collateral damage".
Energy weighs on the S&P 500 on Thursday.
The S&P financial index fell 1.4 percent, among the biggest drags on the S&P 500.
Brent crude futures fell 8 cents to $72.20 a barrel and US crude futures were down 2 cents at $66.92 a barrel.
The S&P 500 plunged 20.30 points, or 0.7 per cent, to 2,833.28. The Nasdaq gained 0.3 per cent for the week after strong gains in some technology shares.
"Any time that there's any movement in currencies, financials tend to reap the contagion risks", said Jamie Cox, managing partner for Harris Financial Group in Richmond, Virginia.
Data on Friday showed US consumer prices rose in July and the underlying trend continued to strengthen, pointing to a steady increase in inflation pressures.
Declining issues outnumbered advancers for a 2.34-to-1 ratio on the NYSE. The tech-heavy NASDAQ was also 0.6 percent lower, ending at 7,839.
Oil prices were down slightly as the escalating China-U.S. trade dispute cast doubt on the outlook for crude demand.