Major US stock indexes reversed early gains and turned sharply lower on Thursday as rising geopolitical tensions between the West and Iran unsettled investor sentiment. Markets moved into negative territory after warnings from Tehran and fresh developments involving the European Union heightened concerns over stability in the Middle East.

Tensions escalated after US President Donald Trump issued new threats, prompting Iran to warn that it would “defend itself and respond like never before.” Adding to the unease, the European Union confirmed its decision to label Iran’s Islamic Revolutionary Guard Corps (IRGC) as a terrorist organisation. The IRGC subsequently announced plans to conduct naval drills in the Strait of Hormuz, a critical global shipping route.

At 10:44 am ET, the Dow Jones Industrial Average was down 0.64%, or 305 points, while the Nasdaq 100 plunged 2.01% at 10:43 am ET, leading the losses among major benchmarks. The S&P 500 also came under pressure, falling 1.24% at 10:42 am ET.

Technology stocks weighed heavily on the market, with Microsoft sliding more than 11% after the company reported a slowdown in cloud growth. The stock led declines across both the Dow and the Nasdaq, dragging broader tech sentiment lower.

Selling pressure was not limited to technology shares. Within the S&P 500, First Solar and Las Vegas Sands plunged over 13%, reflecting broad-based risk aversion across sectors.

The sharp reversal in US equities comes amid heightened volatility across global markets, with investors closely monitoring geopolitical developments and corporate earnings for further direction.