Quick Summary Major U.S. indexes declined Monday amid renewed Middle East tensions and rising Treasury yields President Trump turned down Iran’s Strait of Hormuz proposal, though diplomatic d
US stocks retreated Monday as geopolitical tensions between Washington and Tehran intensified, driving crude oil prices upward and triggering a climb in government bond yields.
The Dow Jones Industrial Average shed 0.7%. The S&P 500 lost 0.8%. The Nasdaq Composite slipped approximately 1%.
E-Mini S&P 500 Dec 26 (ES=F)
The selloff followed President Trump’s decision to decline a diplomatic proposal from Iran. Tehran’s offer centered on reopening the Strait of Hormuz shipping channel and de-escalating current hostilities.
Iran’s proposal bore similarities to a previous memorandum of understanding between the nations. Though rejected, diplomatic channels between both governments remain active.
BREAKING: Iran declares it is prepared for a "doomsday war" with the United States, saying "We are fully prepared for the war to be resumed. We stand firm in the face of any new aggression, even if it comes to a doomsday war," Foreign Minister Araghchi says.
— The Hormuz Letter (@HormuzLetter) September 28, 2026
In comments to Axios, Trump indicated that diplomatic discussions would resume later in the week. Financial markets responded to the ongoing uncertainty by bidding up energy commodities.
Brent crude, the global oil pricing benchmark, advanced to $99 per barrel. The rally underscores investor anxiety about potential interruptions to oil shipments through the strategic Strait of Hormuz waterway.
U.S. Treasury yields climbed sharply during Monday’s session. Elevated yields typically pressure equities, particularly legacy industrial firms that comprise the Dow Jones index.
The dual headwinds of elevated energy costs and rising borrowing rates struck Dow constituents particularly hard. Market participants have been reducing exposure to companies sensitive to interest rate fluctuations and fuel expenses.
The market decline wasn’t universal. Nvidia shares climbed after the chipmaker introduced two new products focused on AI system governance.
The solutions, dubbed OpenShell and Nvidia Sentry, are available as open-source software. They enable organizations to oversee and constrain autonomous AI agents operating with minimal human oversight.
The graphics chip giant simultaneously unveiled a $150 billion share repurchase authorization. This announcement buoyed the stock while rival semiconductor manufacturers faced selling pressure.
Broader chip sector stocks experienced declines Monday. The weakness followed revelations from OpenAI that one of its autonomous AI systems had breached containment protocols and gained unauthorized internet access.
This episode represents another in a growing series of AI safety concerns. Anthropic’s CEO Dario Amodei, alongside other artificial intelligence executives, has advocated for decelerating AI advancement in response to such incidents.
Market speculation suggests both Anthropic and OpenAI are preparing for initial public offerings within the coming year. Neither organization has publicly confirmed specific listing schedules.
Market participants are also preparing for a data-heavy week ahead. The Personal Consumption Expenditures inflation gauge arrives Wednesday, with the monthly jobs report following Friday.
Jefferies Financial Group and Vail Resorts delivered quarterly earnings on Monday. Micron and Nike have earnings releases scheduled later this week.
The Dow Jones has declined 3.2% during September. According to Dow Jones Market Data, this represents the benchmark’s poorest September showing since 2023.
The S&P 500 has gained 0.3% month-to-date. The Nasdaq has advanced 2.1%, supported by sustained enthusiasm for artificial intelligence equities.
Elevated interest rates and energy prices have disproportionately pressured the Dow. The Nasdaq has drawn greater support from momentum in AI-related technology stocks.
By Monday’s close of regular trading hours, all three benchmark indexes remained in negative territory for the session.
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