President Trump recently blamed Ukrainian attacks on Russian refineries for surging diesel prices, but analysts say the Iran war is probably a bigger factor. U.S. diesel prices are up about 65 percent since Feb. 28, when U.S.-Israel attacks on Iran began, topping $6.23 a gallon by Monday. Gasoline is up 45 percent to $4.31, and global oil is up about 50 percent.

"We have basically two wars involving two of the world's largest energy producers," said Helima Croft of RBC Capital Markets. "The Middle East is the most prolific energy production zone, and then you add Russia into this."

Trump and his aides have sought to focus attention on Ukraine's strikes on Russian refineries, away from the Iran war. Ukrainian strikes have forced the Kremlin to suspend diesel exports. But even Russian officials acknowledge refinery attacks are not the central driver. Kremlin spokesman Dmitri S. Peskov said Russia's oil markets were "deteriorating rapidly, mainly due to instability and further rounds of escalation in the Persian Gulf region."

Diesel supply from Russia and the Middle East has effectively collapsed. Russian exports have fallen around 90 percent and Middle Eastern diesel exports are down around 75 percent, according to Pickering Energy Partners. On Friday, Saudi Arabia shut down a critical pipeline as a precaution against Houthi attacks. Iran has effectively closed the Strait of Hormuz.