US Stocks Close Mixed as Investors Track Iran Conflict; Micron Slides 6%

US stocks ended mixed.

On May 18, the Dow Jones Industrial Average rose 159.95 points, or 0.32%, to 49,686.12 on the New York Stock Exchange. The S&P 500 fell 5.45 points, or 0.07%, to 7,403.05, while the tech-heavy Nasdaq Composite dropped 134.41 points, or 0.51%, to 26,090.73.

Technology and semiconductor shares led the declines and weighed on the broader market. Seagate and Micron fell about 7% and 6%, respectively, while SanDisk dropped 5.3%.

The S&P 500 information technology sector lost about 1%, and the Philadelphia Semiconductor Index fell 2.5%.

Profit-taking after the recent rally added to selling pressure. Investor caution ahead of Nvidia's earnings report on May 20 also weighed on chip stocks. Trump's visit to China raised questions about Taiwan's defense, fueling supply-chain concerns and prompting investors to lock in gains in semiconductor shares.

Markets received mixed signals on the Iran war, swinging between disappointment and hope. Media reports said the US viewed Iran's latest proposal as only a formal step forward from earlier positions and insufficient to reach an agreement.

The S&P 500 and other indexes pared some losses later in the day after President Donald Trump said he would delay military action against Iran.

Trump wrote on Truth Social that he had instructed the military not to carry out the attack on Iran that had been scheduled for May 19.

He added that the military should be prepared to launch an immediate, full-scale and major attack on Iran if an acceptable agreement is not reached.

International oil prices extended gains on concerns the war could drag on. Brent crude for July delivery rose 2.60% to settle at $112.10 a barrel, while US West Texas Intermediate futures climbed 3.07% to $108.66 a barrel.

Both benchmarks rose for a third straight session. Brent posted its highest close since May 4, while WTI reached its highest close since April 7.

US Treasury yields jumped before ending little changed. The benchmark 10-year Treasury yield climbed as high as 4.659% in overnight trading, the highest since February 2025.

It later gave up those gains in regular trading as sellers emerged at higher levels. The yield ended near 4.591%, roughly unchanged from the previous day.

The dollar weakened as Treasury yields eased. Reuters reported that the dollar index, which tracks the greenback against major currencies, fell 0.33% to 99.03.

Ko Jeong-sam, Hankyung.com reporter jsk@hankyung.com