About 15 minutes into trading, the Dow Jones Industrial Average stood at 23,383.10, down 1.4 per cent.
The broad-based S&P 500 dropped 1.0 per cent to 2,801.24, while the tech-rich Nasdaq Composite Index shed 0.6 per cent to 8,558.01.
Buffett said over the weekend he had sold large equity stakes American Airlines, Delta Air Lines, Southwest Airlines and United Airlines, commenting, “The airlines business, I think, changed in a very major way.”
Shares of the four companies were down between six and 10 percent.
The move added to worries of a slow US economic rebound following coronavirus shutdowns that have devastated tourism and several other sectors.
Analysts said investor sentiment has also been pressured by revived US-China trade worries amid a squabble over the origins of the coronavirus.
This week’s economic calendar includes the closely-watched April jobs report, as well as earnings reports from General Motors, Disney and others.