(CNN) -- A sharp increase in the price of North Sea oil helped drive U.S. gasoline prices up about 12 cents a gallon since late January, according to a new nationwide survey.

The latest Lundberg Survey found the average price of regular gasoline rose to $3.51 per gallon, publisher Trilby Lundberg said Sunday. The survey canvasses about 2,500 filling stations in the continental United States twice a month.

West Texas Intermediate crude, the U.S. benchmark fuel, remained largely flat between Jan. 20 and Friday, when the most recent survey was conducted. There's a glut of the fuel on U.S. markets, so its price went up only 21 cents a barrel between surveys, Lundberg said.

But Europe's benchmark Brent crude -- another fuel commonly used in American gasoline -- traded up by $7.45 per barrel over the same period. Lundberg blamed the jump on reduced production from North Sea platforms, tensions among Iran, its Persian Gulf neighbors and Western powers and a dispute between Sudan and newly independent South Sudan that has cut off southern oil from global markets.

"Brent is highly sensitive to these events," she said.

Meanwhile, U.S. retailers have little margin to absorb the increased fuel prices, meaning pump prices may edge up "a few more pennies" in the coming weeks, Lundberg said.

The lowest prices in the latest survey were in Denver, where regular gas cost an average of $3.01 a gallon. The highest were on New York's Long Island, at $3.82.

Average prices in some other cities:

Atlanta: $3.54

Baltimore: $3.52

Billings, Montana: $3.03

Boston: $3.60

Chicago: $3.63

Houston: $3.42

Jackson, Mississippi: $3.38

Las Vegas: $3.41

Minneapolis: $3.45

Portland, Oregon: $3.48