Oil prices rose 5% on Monday after the United States reinstated its blockade of Iranian shipping in the Strait of Hormuz, with Brent crude climbing to $79.37 per barrel. The United States announced it would impose a 20% toll on cargo passing through the strait to cover safety and security costs, according to President Donald Trump, who said the arrangement would begin immediately and that the country would be known as the “guardian of the Hormuz Strait,” a phrase quoted in a social media post. The United States launched additional missile strikes against Iranian targets on Sunday, saying the action was intended to degrade Iran’s ability to attack civilian mariners and commercial ships, a statement from U.S. Central Command said. Iran’s Islamic Revolutionary Guard Corps reported that it halted two vessels in the strait by shutting down their systems, though it did not name them. The number of ships transiting the strait fell to six on Sunday, the lowest in five weeks, according to data analyst Kpler. Kpler also reported that tankers exiting the strait included the very large crude carrier Humanity, which carried 2 million barrels of Iranian oil, and the tanker Capetan Andreas, which carried about 500,000 barrels of Kuwaiti oil products. Three empty tankers entered the Gulf to load oil. Most vessels turn off transponders when crossing the strait. Iran said it had closed the strait after a vessel used an unapproved route; the United States said the route remained open to commercial traffic. The escalation has cast doubt on an interim truce signed between the United States and Iran last month. Analysts at Goldman Sachs noted that recent attacks increase uncertainty about Gulf exports and could raise short‑run oil price risk. Gold fell 1.4% to $4,083 per ounce on Monday as higher oil prices raised concerns about inflation and potential interest rate hikes. OPEC lowered its forecast for global oil demand growth in 2026 to 780,000 barrels per day, the third consecutive downward revision, while the International Energy Agency expects demand to decline by 1 million barrels per day in the same year. Stock markets reacted to the developments: the Nasdaq fell 1% and the S&P 500 slipped 0.4% in the United States, while South Korea’s Kospi dropped 8% and Japan’s Nikkei 225 and China’s Shanghai Composite each fell about 2%. Chip manufacturers also declined, with SK Hynix down 15% and Samsung down 10%. The situation remains unresolved as the United States and Iran continue to exchange statements and military actions, leaving the flow of Gulf oil uncertain.