The broader Standard & Poor's 500 index fell 0.5%, the Dow Jones Industrial Average fell 366 points, or 0.8%, and the Nasdaq Composite index fell 0.3%.

Concerns are growing about the potential repercussions of US tariffs on the US economy, particularly after last week's worse-than-expected labor market report. However, hopes for upcoming interest rate cuts by the Federal Reserve and a stream of stronger-than-expected earnings reports from major US companies are helping to calm concerns.

US tariffs went into effect this morning. Some countries are still trying to negotiate a reduction in the tariff rates on their exports, and uncertainty appears to be continuing.

Meanwhile, the latest reports on the US economy have been mixed, leaving Treasury yields relatively stable in the bond market.