(Updates with index/price moves and company/geopolitical news from the first paragraph.)
US equity indexes fell after President Donald Trump said he plans to reinstate a blockade on Iranian ships transiting the Strait of Hormuz while proposing a toll for cargo using the chokepoint for about a fifth of global crude oil flows, sending crude oil and Treasury yields sharply higher.
The Nasdaq Composite dropped 1.4% to 25,921.3, with the Dow Jones Industrial Average down 0.3% to 52,505.5 and the S&P 500 lower by 0.6% to 7,529 after midday Monday.
Technology led decliners, while energy topped advancers. Chevron (CVX) was the Dow's second-biggest gainer, up 2.6%.
On Sunday, the US Central Command said it completed a new wave of strikes against Tehran at multiple locations, after conducting attacks a day earlier in response to the country targeting another commercial ship transiting through the Strait of Hormuz. Iran responded by targeting US military facilities in Jordan, Kuwait, Bahrain, Qatar, and Oman, according to local state media.
Iranian ships will not be able to travel through the Strait of Hormuz, media reports cited Trump as saying on Monday. The US will act as "THE GUARDIAN OF THE HORMUZ STRAIT" and will receive reimbursement for all incurred costs "at the rate of 20% on all cargo shipped," Trump said Monday on Truth Social. He said the strait is open and will remain so for all non-Iranian vessels.
The front-month global benchmark North Sea Brent surged 6.5% to $80.91 a barrel, and the US West Texas Intermediate jumped 6.4% to $75.97 a barrel.
"Oil prices jumped, with Brent trading near USD 80 per barrel, after the battle for control over the Strait of Hormuz escalated over the weekend," Saxo Bank said in a note. "Fresh strikes by US and Iran renewed concerns about the safe passage of oil and other key commodities through the narrow waterway."
"The hostilities also risk derailing efforts to rebuild inventories, according to the IEA, while further reducing the prospects for a diplomatic resolution," the note said.
US Treasury yields rose, with the 10-year up 4.5 basis points to 4.61% and the two-year jumped 6.1 basis points to 4.27%.
In precious metal markets, gold futures slumped 2.8% to $4,003.2, and silver futures sank 3.8% to $57.88.
In company news, SK Hynix (SKHY) Chief Executive Kwak Noh-Jung expects the global shortage of memory chips to persist beyond 2030 as demand driven by artificial intelligence continues to outpace supply, Bloomberg reported Friday. Shares were down 6.9% on Monday, following the company's Nasdaq debut Friday.