Iran's oil supplies have registered a sharp decline since the tightening of the US naval blockade and the near-total closure of the Strait of Hormuz, which has also paralyzed the movement of oil and slashed exports by Gulf producers, the monthly report of the Organization of the Petroleum Exporting Countries (OPEC) revealed on Thursday. Iran’s crude oil production slumped by 19% last month, according to data from OPEC, while the US blockaded the country’s ports during their ongoing conflict. Iran was the primary contributor to last month’s sharp decline. The cartel reported that Iranian output fell by 19%, or 546,000 barrels, to 2.33 million. The blockade of the Strait of Hormuz has also affected collective regional figures. Crude oil production by OPEC declined by 177,000 barrels per day (bpd) in May compared with April, driven mainly by a sharp drop in Iranian output, while the group maintained expectations for stronger global oil demand growth in 2026. Total OPEC crude production averaged 33.13 million barrels per day in May, down by 185,000 daily barrels from the previous month. The 11-member group trimmed its forecast for global oil demand growth this year to 970,000 barrels per day, citing geopolitical conflict in the Middle East. OPEC had predicted 1.17 million barrels in the previous report. Meanwhile, OPEC maintained an optimistic outlook for the near future, betting that post-shock energy demand will rapidly rebound. It raised its 2027 global oil demand growth forecast to 1.73 million bpd, up from the previous projection of 1.54 million bpd. OPEC's June 2026 monthly report described the global economy's first-half performance as resilient despite the geopolitical environment, leaving its macroeconomic growth forecasts unchanged alongside the demand revision.