S&P 500 Falls as AI Slowdown Calls and a US-Iran Deal Rattle Markets

U.S. stocks declined on Monday, September 14, with the S&P 500 finishing down 0.5% and the Nasdaq Composite falling 0.6%, as two major forces hit investor sentiment simultaneously: calls from top AI executives for a global slowdown in artificial-intelligence development, and a sharp drop in oil prices after the United States and Iran announced an agreement to end hostilities and reopen the Strait of Hormuz.

Anthropics CEO Dario Amodei published an essay urging AI labs to slow the pace of model capability gains, citing risks from AI self-improvement and recent safety incidents. OpenAI CEO Sam Altman and xAI's Elon Musk quickly backed the proposal, as did Hugging Face CEO Clement Delangue. The coordinated call alarmed investors who had priced in sustained, aggressive AI infrastructure spending, dragging chipmakers and AI-dependent stocks lower. Micron Technology fell approximately 5.9% to $918.36, with analysts noting the company carries a roughly $50 billion quarterly revenue target that leaves little margin for any pullback in AI investment. GE Vernova sank 8.6%, compounding an earlier 4.8% pre-market drop after GLJ Research initiated coverage with a Sell rating and a $470 price target, a stark contrast to the broadly positive analyst consensus on the stock.

The US-Iran deal, which included reopening the Strait of Hormuz to shipping, sent crude oil prices sharply lower, unwinding a supply-risk premium that had driven Brent crude up nearly 9% the prior week toward $106 a barrel. SLB, the oilfield services giant, fell roughly 4% to around $53.91 as investors calculated that lower oil prices would prompt producers to cut drilling budgets, reducing demand for SLBs services. BlackRock and Cava Group also closed below the broader market, while Sionna Therapeutics and Kestra Medical Technologies declined on company-specific pressures.

Not every stock followed the market lower. AstraZeneca and Microsoft both gained on the day, as did Altria, with defensive and healthcare names attracting buyers seeking shelter from the technology and energy sector volatility. The Federal Reserve is set to meet later in the week, with traders pricing in a near-certain quarter-point rate hike from Chairman Kevin Warsh, adding a further headwind as US 10-year Treasury yields have risen above 5% for the first time since 2023.