The Wall Street benchmarks slumped more than 1% on Thursday as investors continue to focus on tensions between the West and Russia over Ukraine, with some disappointing earnings also weighing on the mood.
All the major S&P sectors were lower in morning trade, with financial and technology stocks falling the most with losses of nearly 2%.
Russia expelled deputy United States ambassador Bartle Gorman, warning of a U.S. response amid heightened fears of a Russian invasion of Ukraine.
Meanwhile, U.S. President Joe Biden said the threat of an invasion is "very high." Russia-backed rebels and Ukrainian forces earlier exchanged fire across a frontline that divides them, in what Western officials described as a possible pretext created by Moscow to invade.
"Every other headline that comes out on Russia-Ukraine, seems to tell a different story. Right now, the narrative seems to be more aligned with the fact that this is getting worse, not better," said Art Hogan, chief market strategist at National Securities.
"Markets right now are clearly the combination of tensions in Ukraine and Russia and inflationary data and what that means in terms of monetary policy."
At 9:58 a.m. ET (2:58 p.m. GMT), the Dow Jones Industrial Average was down 422.34 points, or 1.21%, at 34,511.93, the S&P 500 was down 55.33 points, or 1.24%, at 4,419.68, and the Nasdaq Composite was down 177.35 points, or 1.26%, at 13,946.75.
Chipmaker Nvidia slid 6.7% as flat gross margins and concern about its exposure to the crypto market overshadowed upbeat current-quarter revenue forecast.
TripAdvisor Inc. slipped 4.4% after the hotel search website operator posted a surprise fourth-quarter loss, while Albemarle Corp. tumbled 16.7% as the lithium producer forecast downbeat annual earnings.
Big banks including JPMorgan Chase, Morgan Stanley and Bank of America slid between 2% and 3.3%, while Goldman Sachs fell 2.3% despite upgrading its key profitability target.
Markets have gyrated this week as geopolitical tensions added to worries about the Federal Reserve's (Fed) tightening plans this year. Losses so far on Thursday put the Dow on track to end the week in negative territory.
Among other big movers, DoorDash Inc. surged 16.4% after it reported upbeat quarterly revenue as food delivery demand showed no sign of slowing, indicating ordering habits have changed permanently.
Hasbro Inc. rose 6.4% after activist investor Alta Fox Capital Management nominated five directors to the toymaker's board and urged changes including a spinoff of its unit housing games such as "Dungeons & Dragons."
Declining issues outnumbered advancers for a 3.00-to-1 ratio on the NYSE and a 3.17-to-1 ratio on the Nasdaq.
The S&P index recorded four new 52-week highs and seven new lows, while the Nasdaq recorded 16 new highs and 81 new lows.