The 72-Hour U.S.-Iran Peace Deal: How a Historic Accord Sparked — Then Lost — a Market Rally

On June 17, 2026, the United States and Iran signed an interim Memorandum of Understanding (MOU) to end hostilities, reopen the Strait of Hormuz, and allow Iran to resume oil sales. The deal triggered a powerful but short-lived market rally. Within three days, Iran announced it had reclosed the strait, sending oil prices back up and plunging the agreement into fresh uncertainty .

What the deal included

The interim agreement was a 60-day MOU that mandated Iran to reduce its stockpile of highly enriched uranium, while the U.S. lifted sanctions on Iranian oil sales and ended its naval blockade of Iranian ports . U.S. Central Command declared on June 18 that American forces had ended the blockade . Iran was permitted to immediately begin selling oil and fuel upon signing . The deal also set the stage for nuclear negotiations over the following two months .

Immediate market euphoria: oil crashes, stocks surge

• Oil prices plunged as the market priced in the reopening of the Strait of Hormuz. Brent crude and other benchmarks lost nearly all of their war-related gains, with oil headed for its longest losing run in 10 months . Goldman Sachs forecast further declines but cautioned that prices were unlikely to return to pre-war levels quickly .
• Asian markets led a global equity rally on Monday, June 15, as investors shed the geopolitical risk premium that had built up over 15 weeks of war .
• On June 18, the S&P 500 climbed 1.1% and the Nasdaq surged 1.21% (315.60 points to 26,337.25) . The Philadelphia semiconductor index reached a record high .

The semiconductor rally: Intel-Apple deal as the catalyst

Chip stocks were the standout performers, driven by a separate corporate catalyst layered on top of the macro optimism:

• Intel shares jumped nearly 10% on June 18 after President Donald Trump announced that Apple had agreed to partner with Intel to design and manufacture semiconductors in the U.S. .
• The Nasdaq's 1.9% advance was powered by semiconductor gains, as the deal helped ease inflation concerns that had been pressuring tech valuations . The Philadelphia semiconductor index surged 6.4% .
• Analysts described the move as a "rebound" — tech stocks had been under pressure from a hawkish Federal Reserve under new Chair Kevin Warsh, and the Iran deal provided cover for a rotation back into growth names .

Why the euphoria unravelled

Within 48 hours, the deal's initial optimism was severely undermined:

• Confusion and denials — On June 19, Iran's foreign ministry denied reports that the strait had been reclosed, while the Persian Gulf Strait Authority said ships with "compliant transit requests" could pass . But the mixed messaging rattled markets.
• Talks delayed — Vice President JD Vance postponed a planned visit to Switzerland for the next round of negotiations, and discussions between U.S. and Iranian representatives were put on hold .
• Iran announces reclosure — On Saturday, June 20, Iran's joint military command announced the Strait of Hormuz was closed again, accusing the U.S. and Israel of violating the peace agreement. The U.S. disputed the claim, insisting the strait remained open .
• Oil prices reversed — After days of declines, oil prices turned volatile and began ticking higher as the deal's durability came into question . The New York Times reported that "oil prices exhibited volatility on Friday as uncertainties surfaced" .

The structural fragility

Analysts at Chatham House warned that even if the deal held, Iran retained the ability to close Hormuz again — and that a simultaneous Houthi disruption in the Bab al-Mandab Strait would be disastrous . The core problem was that the interim agreement was a fragile 60-day truce with no enforcement mechanism, leaving markets to oscillate between relief and renewed fear with each contradictory headline out of Tehran.