American oil executives warned for months that the prolonged closure of the Strait of Hormuz was bound to cause a fuel crisis. Now, they say it is here.

Commercial fuel stocks around the world have been depleting for more than six months, and strategic crude reserves can’t be tapped much further. Attacks last week shut down a crucial crude pipeline in Saudi Arabia that bypassed the Strait, stranding at least 2.5 million barrels a day from an already tight global oil market, analysts estimate.

“All these mechanisms helped to mitigate the price and supply risk,” Chevron CVX 1.94%increase; green up pointing triangle Chief Executive Mike Wirth said Friday at an energy conference in Austin, Texas. “Those have largely now played out, and we don’t have nearly the buffers in the system that we did when it began.”