U.S. retail gasoline prices should be high for much of July, bucking a seasonal trend, a spokesman for motor club AAA said.

"It is shaping up to be a hot and expensive summer for gas prices, and we have not even hit the busiest time of the year yet," AAA spokesman Avery Ash said in a Monday report. "It is clear that most drivers will pay high prices as they fill up for their summer road trips."

The monthly national average price for a gallon of regular unleaded gasoline was $3.67 last month, the most expensive June in three years. Gas prices usually decline in June because refiners produce more gasoline in anticipation of higher summer demand, though conflict in Iraq has kept prices elevated.

During the last three years, the national average price per gallon declined by an average 21 cents in June.

"Most drivers are paying about 15-20 cents more per gallon than expected heading into the busy Independence Day weekend due to market fear about Iraq," Ash said.

Tuesday's national average price was $3.67, nearly 20 cents higher than the same time last year. AAA said the price at the pump for the U.S. holiday weekend may be the highest since 2008.