June 18 (UPI) -- The average price of a gallon of regular gas in the United States dropped below $4 Thursday, marking the first time prices have been this low since March 30.

U.S. average retail gasoline prices dipped below $4 a gallon for the first time since mid-April, as optimism grew that a preliminary deal ​between the U.S. and Iran would lead to the reopening of the Strait of Hormuz.