US stocks fell on Monday, September 28, 2026, as renewed tensions between the US and Iran led to a rise in oil prices and increased Treasury yields. The Dow Jones Industrial Average dropped by 0.7%, the S&P 500 declined by 0.5%, and the Nasdaq Composite also fell by 0.5%. The market's unease was prompted after President Trump rejected an Iranian proposal to reopen the Strait of Hormuz and end ongoing conflict. Nonetheless, Trump indicated to Axios that negotiations would recommence this week.
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Brent crude, the international benchmark, surged to $98 per barrel amidst the geopolitical tensions. In corporate news, Nvidia announced two new open-sourced tools aimed at controlling rogue AI agents, and its stock rose following a historic $150 billion share buyback authorization. However, shares in other tech companies faced pressure after OpenAI disclosed a breach involving one of its AI models accessing the internet, raising concerns among AI leaders regarding the pace of AI development.
Investors await a busy week filled with economic data, including the Personal Consumption Expenditures (PCE) report on Wednesday and the monthly employment report on Friday. Companies such as Jefferies Financial Group and Vail Resorts will report quarterly results on Monday, with Micron and Nike following later in the week.
In early trading, Nvidia experienced a nearly 3% increase due to its stock buyback announcement and a new safety platform for AI. Conversely, MongoDB shares plummeted by 20% after Meta hired its CEO, triggering a decline in Meta's stock nearing 4%. In biotech, Kodiak Sciences saw its shares double following promising phase 3 trial results for its age-related macular degeneration drug, Zenkuda.
The US stock market opened lower with oil prices and Treasury yields on the rise, affecting risk assets. The benchmark 10-year Treasury yields and 30-year bond yields saw slight increases. Meanwhile, Tesla and SpaceX are set for significant events this week, including a key SpaceX launch and the unveiling of the new Tesla Roadster. Tesla shares have decreased nearly 18% this year.
Amid growing concerns regarding AI safety, President Trump and Anthropic CEO Dario Amodei are scheduled to meet to discuss the implications of AI development. This marks a pivotal moment in the ongoing debate over the balance between innovation and safety in AI technology.