05:05 PM EDT, 03/26/2026 (MT Newswires) -- The S&P 500 declined the most since January on Thursday as oil prices jumped amid uncertainty around the prospects of a ceasefire between the US and Iran.

The S&P 500 fell 1.7% to 6,477.2, it's biggest one-day decline since Jan. 20. The Nasdaq Composite closed 2.4% lower at 21,408.1. The Dow Jones Industrial Average lost 1% to settle at 45,960.1.

Most sectors were in the red, led by communication services' 3.5% slump.

West Texas Intermediate crude oil was last up 2.8% at $92.82 per barrel, while Brent climbed 3.1% to $100.24.

After the closing bell, President Donald Trump said the US was further delaying strikes on Iran's energy infrastructure by 10 days, following an initial five-day postponement. He claimed in a social media post that Tehran requested the extension.

While prospects of peace talks have emerged, conflicting signals from Washington and Tehran have fueled doubts that an end to the four-week-long war is near.

Trump said it's up to Iranian leaders to convince him to end the Middle East conflict, CNN reported Thursday. Trump said he doesn't care about striking a deal with Iran, adding that the US has additional targets "to hit before we leave."

Israeli Defense Minister Israel Katz reportedly said Iranian Navy Commander Alireza Tangsiri has been killed. Katz said that Tangsiri was a key figure behind the near-total blockade of the Strait of Hormuz, the world's most important chokepoint for crude flows.

Brent crude prices could surge to $150 a barrel if the Strait of Hormuz remains shut for another month, possibly worsening supply disruptions, analysts said.

US Treasury yields were higher, with the 10-year rate last up 8.1 basis points at 4.42% and the two-year rate gaining nine basis points to 3.99%.

In economic news, the Organization for Economic Co-operation and Development said a prolonged period of high energy costs will substantially drive up consumer inflation globally, with price growth in the US seen hitting 4.2% this year.

"Faced with the energy price shock, central banks need to remain vigilant and ensure that inflation expectations stay well anchored," the OECD said. "Monetary policy adjustments may be needed if price pressures broaden or if growth prospects weaken substantially."

Weekly applications for unemployment insurance in the US increased as Oxford Economics cautioned that the Middle East conflict has made the labor market "vulnerable."

In company news, Lumentum ( LITE ) said it plans to set up a facility in Greensboro, North Carolina, to produce advanced indium phosphide-based optical components used in large-scale artificial intelligence data centers, with Nvidia ( NVDA ) among the expected customers.

Lumentum ( LITE ) shares slid 11%, the worst performer on the S&P 500, while Nvidia ( NVDA ) fell 4.2%, the steepest decline on the Dow.

Commercial Metals ( CMC ) reported fiscal second-quarter earnings below market estimates, though revenue surpassed expectations amid gains across all business segments. The metal products manufacturer's shares slumped 4.7%.

French beverages firm Pernod Ricard is weighing a potential acquisition of US wine and spirits maker Brown-Forman (BF.A, BF.B), Bloomberg News reported, citing unnamed sources. Brown-Forman's class B shares surged 9.6%, the top gainer on the S&P 500, while its class A shares jumped 8.9%.

Gold was last down 3.5% at $4,426.80 per troy ounce, while silver slumped 6% to $68.28 per ounce.