03:56 PM EDT, 07/16/2026 (MT Newswires) -- (Updates with index/price moves and geopolitical news from the first paragraph.)

US equity indexes dropped as a sell-off in chipmakers pushed technology sharply lower, and Iran threatened to close the Red Sea crude oil route if President Donald Trump orders an attack on Tehran's power infrastructure.

The Nasdaq declined 1.8% to 25,786.2, the S&P 500 fell 0.8% to 7,508.7, and the Dow Jones Industrial Average declined 0.5% to 52,386.8.

Technology slumped 2.3%, the worst of a trio of decliners in the final leg of trading.

Shares of Taiwan Semiconductor Manufacturing ( TSM ) slid 3.1% after the firm earmarked an additional $100 billion to increase its chipmaking capacity in the US, raising its total planned investment to $265 billion, Bloomberg reported Thursday, citing a US official. Taiwan Semiconductor also reported Q2 results on Thursday, with year-over-year earnings and net revenue rising and Q3 sales guidance beating consensus.

Among stocks with market capitalization exceeding $200 billion each, 15 out of the bottom 20 names were from the technology sector, according to data compiled by Finviz. Half of the decliners were semiconductor firms, the data showed. The worst performer was SanDisk ( SNDK ) , down 11%.

In company news, UnitedHealth's ( UNH ) shares jumped 3.1%, making it one of the Dow's top gainers, after the company posted higher Q2 adjusted earnings and revenue and raised its 2026 adjusted EPS outlook.

In geopolitical news, the US military launched a sixth consecutive night of strikes on Iran, with the country's media reporting explosions on Qeshm Island, Bandar Abbas, and Chabahar, according to Al Jazeera, a Middle Eastern broadcaster.

The Iranian military has warned "all infrastructure in the region will be crushed under steel blows" if the US carries out its threat to attack Iran's civilian sites, the Al Jazeera report said. Iran has asked Yemen's Houthi movement to stand ready to close the Red Sea oil route if the US strikes Iranian power infrastructure, Reuters reported, citing three sources.

Total volumes of petroleum transiting Bab el-Mandeb amounted to 7.4 million barrels per day in June, or about 7% of global oil output, up from 4.2 million bpd a year ago, MarineLink reported, citing Kpler data.

The front-month US West Texas Intermediate fell 0.7% to $79.08 a barrel, hovering around its highest in about a month amid a rally that began after the US renewed strikes on Iran a week ago. North Sea Brent futures retreated 0.7% to $84.34 a barrel, close to its month-high.

Iraqi crude loadings more than doubled to average roughly 1.2 million barrels per day in the first half of July, Reuters reported, citing Kpler data and a source with direct knowledge of the flows, as exports accelerated following months of restricted shipments.