The average retail price of a gallon of gasoline in the United States rose again over the past two weeks, continuing recent hikes that do not appear to be easing as crude oil prices increase and other market changes kick in, an industry analyst said on Sunday.

The national average for self-serve, regular unleaded gas was $2.3319 per gallon on January 20, up 3.11 cents per gallon since the last nationwide Lundberg survey of gas stations on January 6.

Prices fell nearly 88 cents per gallon between September 9, when they peaked at a record of $3.0117 per gallon, and December 2 when they bottomed out, survey editor Trilby Lundberg said, though they have risen steadily since.

A year ago, the January 21, 2005, survey had the price for a gallon of self-serve, regular unleaded at $1.8747.

"Prices are much more likely to continue rising than to show no change or decline," Lundberg said. "Retail gasoline only having climbed 3 cents will take upward pressure from crude if crude does not fall."

Prices were already expected to rise over the next few months, Lundberg said, driven by required fuel reformulations, provisions in last year's energy bills taking effect, and the renewed rise of crude oil.

U.S. crude prices gained 2.2 percent to $68.35 a barrel on Friday in New York after al Qaeda threats added to worries about supplies from crude exporters in Iran and Nigeria. Oil prices have gained 23.4 percent since their five-month low of $55.40 hit in mid-November.

At $2.80 a gallon, Honolulu had the highest average price for self-serve, regular unleaded gas, while the lowest price was $2.10 a gallon in Portland, Oregon.