Oil prices sharply on Friday as reports that some tankers were forced to turn around in the Strait of Hormuz prompted traders to reassess shipping flows through the key waterway.
Oil prices rose sharply in July, with Brent crude headed for monthly gains for the first time since March.
"The shock absorbers in oil markets are dwindling fast, so a failure to de-escalate would be materially costlier than previous rounds of tension," wrote Teddy Bunzel, head of Lazard Geopolitical Advisory at Lazard Asset Management.
Shipments through the crucial Strait of Hormuz remain disrupted. The alternative route through the Bab el-Mandeb Strait has also come under attack from the Iranian-backed Houthis, further worsening the outlook.
Stocks had rallied earlier in the session after strong earnings from Amazon and Microsoft eased investor jitters and drew traders back into the AI trade, but hawkish Fed commentary and rising yields eroded those gains.
Microsoft on Wednesday forecast strong cash generation through fiscal 2027. Amazon followed a day later with its strongest cloud growth in more than four years, reassuring investors eager for proof that massive AI spending is paying off.
"There's significant drawdowns over the course of the month and everything related to artificial intelligence," said Art Hogan, chief market strategist at B Riley Wealth.
"Now with the hyperscalers, in particular Amazon, coming out and talking about the amount of revenue and demand for their cloud services, which in general is a lot of the small and medium businesses, that's put a significant interest back into the neo-cloud companies and their offerings as it pertains to rollout of AI strategies."
The Dow Jones Industrial Average was last down 0.06% at 52,179.23, the S&P 500 fell 0.02% to 7,435.72 and the Nasdaq Composite rose 0.19% to 25,170.38.
The pan-European STOXX 600 index fell 0.03%, while Europe's broad FTSEurofirst 300 index also dipped 0.03%.
South Korea's battered KOSPI leapt 17.91%, mounting a record comeback after heavy losses earlier this week. The tech-heavy bourse, still about 30% off its all-time high, has become emblematic of the sharp swings in investor sentiment towards AI-related stocks.
MSCI's gauge of stocks across the globe was up 0.73% at 1,115.07.