US Stocks Fall as Iran Truce Expires and Oil Prices Surge

US stock markets declined on August 17 and 18, 2026, as the expiration of a 60-day truce between the United States and Iran fueled inflation fears and energy price volatility. Donald Trump refused to extend the ceasefire and denied that any diplomatic conversations were occurring with the Islamic Republic of Iran. In response, Iran characterized the truce as irrelevant and threatened a fully offensive military posture, including keeping the Strait of Hormuz closed.

These geopolitical tensions pushed Brent crude oil prices above $90 per barrel and drove 10-year Treasury yields to 4.72%, the highest levels since 2007. The surge in borrowing costs disproportionately impacted high-growth technology assets. The Nasdaq Composite led the decline, falling 1.3% as investors questioned the valuations of artificial intelligence stocks. Micron Technology dropped 7%, while Broadcom and Nvidia also saw significant losses amid concerns that demand for data center infrastructure might diminish.

Market volatility coincided with corporate shifts, including the departure of L3Harris Technologies CEO Christopher Kubasik due to conduct inconsistent with company values. Investors also monitored the Federal Reserve System, with Chairman Kevin Warsh expected to provide limited guidance on interest rates at the Jackson Hole symposium to combat the rising inflation driven by energy costs.