Apple shares were down after the tech giant was slapped with a €13bn tax bill by European Union regulators today.
The company's Nasdaq-listed shares were down around 0.67% to 106.10 US dollars per share (€94.90).
It followed a ruling by the EU Commissioner for Competition which accused Apple of securing unfair tax deals in Ireland that amounted to state aid.
Apple was found to only be paying 1% tax on its European profits in 2003 and 0.005% in 2014.
Jasper Lawler, a market analyst at CMC Markets, said the news was impacting American equity markets.
"US stocks dropped in early trading as Apple's European tax problems weighed on broader sentiment," he said.
The Nasdaq Composite was down 0.26%, the Dow Jones Industrial Average fell 0.35% and the S&P 500 dropped 0.28%.