NEW YORK — The latest shudder for stocks in the artificial-intelligence industry pulled markets lower worldwide on Thursday, while oil prices hit their highest levels since May on worries about the war with Iran.

The S&P 500 fell 1.2% for its worst day since July, while the Nasdaq composite tumbled 2.6%. The weakness for tech stocks was so overwhelming that it masked strength for the rest of the U.S. market, where the majority of stocks actually rose. The Dow Jones Industrial Average added 11 points, or less than 0.1%.

AI-related stocks have been swinging on worries that their boom may be under threat because of how expensive it’s become to borrow money to build data centers and buy more AI chips. Concerns also remain that their…