Mumbai, July 20 -- Drops for computer chipmakers and other winners of the artificial-intelligence boom dragged down stock markets worldwide on Thursday.

The S&P 500 fell 0.5% even though more stocks rose within the index than fell. The Dow Jones Industrial Average dipped 105 points (0.2%) and the Nasdaq composite sank 1.5%.

Oil prices are near their highest in a month because of worries that the war with Iran will keep oil tankers out of the Strait of Hormuz and prevent shipments of crude from the Persian Gulf to customers worldwide. The price for a barrel of Brent crude briefly climbed above $86 per barrel in the morning before erasing the gain and falling back to settle at $84.23, down 0.8% from the day before.

Reports written on the...