At an energy conference in Austin, Texas, on Friday, Chevron CEO Mike Wirth warned that a fuel crisis delayed by drawing down global oil reserves has finally arrived.

Wirth discussed the drawdown of both commercial reserves and national strategic reserves since the U.S.’s war with Iran began in late February, according to the Wall Street Journal. Global oil supplies have also further tightened after Iranian attacks shut down a Saudi Arabian pipeline to route oil around the contested Strait of Hormuz.

“All these mechanisms helped to mitigate the price and supply risk,” Wirth said, according to the Wall Street Journal. “Those have largely now played out, and we don’t have nearly the buffers in the system that we did when it began.”

Diesel prices have recently surged to an all-time high, hitting an average of $6.27 on Sept. 15, according to AAA data. The average diesel price this time last year was $3.69. Global oil prices have also been rising this month, pushing above $100 per barrel in recent weeks.