New Delhi, June 18 -- US gasoline prices dipped below $4 a gallon for the first time since March, providing welcome relief to consumers after a historic global supply disruption sent fuel costs soaring for months.

National regular unleaded gasoline averaged $3.999 on Thursday, according to the American Automobile Association. The swing down in prices comes as the US and Iran signed an interim deal to end the war and reopen the Strait of Hormuz.

Pump prices have retreated from their May peak above $4.50 a gallon, helped by a decline in global crude prices. Oil has come under pressure, sliding below $80 a barrel, due to a combination of record US exports, a sharper-than-expected slowdown in Chinese demand, and a steady trickle of shipment...