U.S. average retail gasoline prices remained unchanged over the last three weeks, as gasoline supply increased and demand did not, according to the latest nationwide Lundberg survey.

The national average price for self-serve, regular unleaded gas was $2.9330 a gallon on June 9, up just two-hundredths of a cent since May 19, according to the survey of about 7,000 gas stations.

At $3.27 a gallon, Honolulu had the highest average price for self-serve regular unleaded gas, while Wichita, Kansas, had the lowest, at $2.66 a gallon, the survey said.

The unusual stability came from a narrower range of crude oil price changes and higher supply, while demand remained flat, survey editor Trilby Lundberg said in a statement.

"If crude oil prices do not shoot back up soon, then gasoline prices will be under pressure to fall a few cents per gallon as supply builds and demand stays steady," Lundberg said.