The average price of gasoline in the U.S. has risen four cents over the past two weeks to $2.29 a gallon for regular grade.

Industry analyst Trilby Lundberg said Sunday that retailers and refiners have upped their prices in response to a rise in the cost of crude oil.

Gas prices are up 13 cents over nine weeks.

The Lundberg Survey found the average price of midgrade gasoline was $2.56 a gallon while premium was $2.78.

The highest average price for regular gas in the contiguous U.S. was $2.80 in San Francisco. The lowest was $1.97 in Tucson, Arizona.

The average price for diesel in Friday's survey was $2.42, up three cents.