Crude oil is the biggest driver ​for fuel prices, and benchmark crude futures have climbed back above $100 a barrel on the intensification of conflict between the U.S. and Iran.

Industries that depend on ​diesel were already feeling the impact when crude oil futures on Thursday hit their highest level since mid-May. Brent settled at $107.63 ⁠a barrel and West Texas Intermediate futures at $102.48 a barrel.

"Every truck, every delivery, every package, every grocery run just got more expensive," GasBuddy analyst Patrick De Haan said ​on social media site X.

"Record diesel prices will impact every cargo, shipment, every delivery Americans are taking, and are likely to reignite inflation up and down the supply chain," ​he said.

The U.S. national average price of diesel on Thursday surpassed $6 a ​gallon for the first time ever, according to price tracker GasBuddy, as the U.S.-Israeli war on Iran and Ukrainian attacks on Russia’s refineries have squeezed supply.

Diesel ‌fuels trucks, trains, ships and heavy equipment that keep global supply chains moving. It is also crucial to running farm equipment.

The latest surge in fuel costs is adding to inflationary pressures that have already strained consumers and businesses this year, creating a political headache for Donald Trump and Republican lawmakers as they seek to defend thin congressional majorities in November's midterm elections.