U.S. diesel prices reached a record $6.23 a gallon by Monday morning, up about 65% since the United States and Israel attacked Iran on Feb. 28. President Trump blamed Ukrainian strikes on Russian refineries, which have forced the Kremlin to suspend diesel and other fuel exports. Energy experts said those attacks have contributed to tighter supplies, but the war in Iran has been the more important driver of energy prices. Regular gasoline reached $4.31 a gallon, up about 45% since the conflict began, while global oil prices rose roughly 50%. Helima Croft of RBC Capital Markets said the simultaneous conflicts involve two of the world’s largest energy producers. Lauren McCarthy is a business reporter for The Times.