All three major indices were firmly in the red after notching some of the biggest single-day gains in history in the prior day.
About 15 minutes into trading, the Dow Jones Industrial Average was down 1.8 per cent at 39,859.39.
The broad-based S&P 500 fell 2.2 per cent to 5,335.61, while the tech-rich Nasdaq Composite Index shed 2.8 per cent to 16,653.99.
The declines came as US consumer inflation contracted 0.1 per cent from a month earlier in a reading that was lower than analyst expectations. Some market watchers said the inflation reading boosts the odds of Federal Reserve interest rate cuts.
But analysts described the inflation reading as a secondary issue early Thursday compared with reverberations from Trumpโs tariff actions on Wednesday, which prompted huge equity rallies in Asia and Europe.