How the U.S.-Iran War Is Reshaping Stock Markets in 2026: Goldman Sachs Analysis

Key Takeaways

• The S&P 500 has declined approximately 1.4% since military operations against Iran commenced, trading roughly 3% beneath its January peak.
• Oil prices continue climbing despite the International Energy Agency’s unprecedented 400 million barrel emergency reserve deployment.
• Commodity futures indicate crude prices may not stabilize to pre-conflict levels until August 2027.
• Goldman Sachs has adjusted economic projections, forecasting accelerated inflation, decelerated growth, and elevated joblessness linked to ongoing hostilities.
• The 10-year Treasury yield climbed 24 basis points to reach 4.23%, marking its highest level in more than a month.

Financial markets are experiencing sustained pressure as the U.S. military engagement with Iran enters its second week, with climbing crude prices, ascending bond yields, and economists revising growth projections downward.

Since late February when U.S. military strikes against Iran commenced, the S&P 500 has shed approximately 1.4%. While the benchmark index remains only about 3% off its January record peak, market analysts caution that extended conflict could intensify downward pressure.

Crude oil prices experienced sharp gains this week following attacks by Iran-aligned forces targeting tanker vessels in the Strait of Hormuz. This critical waterway handles approximately 20% of global daily oil shipments. Wednesday alone witnessed three separate vessel strikes in the region.

In an unprecedented response, the International Energy Agency authorized the release of 400 million barrels from strategic petroleum reserves to address supply disruptions. Nevertheless, futures trading suggests market participants don’t anticipate prices returning to pre-conflict levels until August 2027.

President Trump announced plans to invoke Defense Production Act authority to resume offshore oil drilling operations along California’s coastline. While Trump previously characterized the conflict as something that would conclude “very soon,” Goldman Sachs alongside other financial institutions are now preparing scenarios for extended disruption.

Economic Projections Deteriorate

Goldman Sachs updated three critical economic forecasts this week, all connected to the Iran situation. The investment bank now projects accelerated inflation, diminished economic expansion, and rising unemployment rates.

Ten-year Treasury yields advanced to approximately 4.23%, representing a 24 basis point increase from late February levels. Thirty-year bond yields reached 4.9% during early Thursday sessions. Market observers attribute this movement to concerns regarding fiscal policy loosening and uncertainty surrounding inflation trajectories and interest rate paths.

The Federal Reserve finds itself in an increasingly challenging position. Elevated oil prices fuel inflationary pressures, potentially compelling the central bank to maintain elevated rates for an extended period, diminishing prospects for rate reductions in 2026.

ING analyst Francesco Pesole suggested that emergency petroleum reserve releases might actually transmit negative signals to financial markets. He indicated this action implies global leadership perceives minimal likelihood of swift conflict resolution.

Military Capabilities and Nuclear Concerns

Iran retains operational short-range missile systems, unmanned aerial vehicles, and naval mining capabilities that can disrupt maritime shipping. Military analysts suggest fully securing the Strait of Hormuz could necessitate ground force deployment—representing significant escalation.

Iran maintains stockpiles of 60% enriched uranium, approaching weapons-grade concentration. Specialists at the Nuclear Threat Initiative caution that should the Iranian government survive the conflict, it may possess both capability and incentive to develop nuclear weapons.

Persian Gulf nations, significantly vulnerable to Iranian military action and reliant on American air defense systems, are expressing private frustration with Washington’s approach. Multiple analysts suggest the region confronts two unfavorable scenarios: an Iran that endures and reconstitutes its capabilities, or a destabilizing power void.

Wall Street firms have not yet modified year-end projections for the S&P 500, which continue forecasting a 14% gain from present levels. However, market watchers note the index has remained confined within a 4% trading band for 14 consecutive weeks.

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