Wall Street stocks dropped early Monday amid escalating tensions between Washington and Tehran after the United States last week killed an Iranian military commander.

File photo: AFP

Iran has threatened to avenge the killing of Qasem Soleimani, while US President Donald Trump vowed more "major retaliation" if Tehran hits back, including strikes on Iranian cultural sites.

About 20 minutes into trading, the Dow Jones Industrial Average stood at 28,514.76, down 0.4 percent.

The broad-based S&P 500 dipped 0.3 percent to 3,226.39, while the tech-rich Nasdaq Composite Index shed 0.3 percent to 8,992.15.

Worries about fallout from the Soleimani killing have shaken markets out of a complacent period in late December that saw Wall Street repeatedly rise to new records amid accommodative monetary policy.

Among individual companies, Boeing fell 1.0 percent on lingering worries about the 737 MAX following a Wall Street Journal report that said US regulators were considering requiring simulator training on the aircraft before allowing it to fly again.

SmileDirectClub, which sells teeth straightening medical devices, surged nearly 10 percent as it sealed a deal to sell a suite of products exclusively at Walmart. Walmart slipped 0.5 percent.