Stocks slipped to start the week as oil prices and bond yields advanced on Monday amid persistent tensions in the Middle East. The 30-year Treasury yield closed at 5.310%, reaching its highest level in nearly 20 years. Yields took a sharper leg up following concerns about a potential escalation in the U.S.-Iran conflict.

Brent crude futures climbed 2.7%, to $90.87 a barrel, after Iranian media reported an oil tanker had been seized in the Strait of Hormuz. The state-linked Fars News Agency noted that Iran requires shipowners transiting the waterway to pay transit fees. The report couldn't immediately be verified. In recent weeks, Iran has taken an increasingly hard-line approach, striking several tankers attempting to pass through the strait.

“The markets have run up so much. Oil needs to come down,” said José Torres, senior economist at Interactive Brokers. “If oil doesn’t come down, then rates stay too elevated and we are subject to a correction.”

Chip stocks advanced, but renewed optimism for the artificial-intelligence trade fell short of lifting major U.S. stock indexes. Some of the market’s biggest gainers included Sandisk, Marvell Technology and Comfort Systems, each up 5% or more.