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The national average price for a gallon of regular unleaded gasoline for Monday is the highest it's been since Sept. 11. Demand may increase along with the price at the pump for April, though a short-term plateau may be within site, AAA said.

Michael Green, a spokesman for AAA, told Oilprice demand for gasoline is expected to increase as a long winter starts to ease across much of the country.

"Given how cold it had been earlier in the year, it would not be surprising to see pent-up demand result in significant gasoline consumption in the coming weeks," he said.

The U.S. Energy Information Administration said demand for gasoline for the week ending March 21 increased 5.7 percent from the previous week to 9 million barrels per day. With winter fading across much of the country, Green said demand should increase as the summer driving season starts to approach.

EIA said in its short-term market report U.S. gasoline consumption increased by 1.1 percent in 2013, the largest increase since 2006. For this year, EIA said consumption should remain relatively static, however, as drivers turn to more fuel-efficient vehicles.

Higher demand typically results in higher prices at the pump.  AAA reports a national average price for Monday at $3.56, the highest daily average since Sept. 11. The average price for a gallon of regular unleaded gasoline increased 49 out of 52 days for a total 29 cents per gallon. AAA said gasoline prices are up primarily because of seasonal refinery maintenance and the switch to the summer blend of gasoline, which is more expensive to produce.

Gasoline prices for March averaged $3.50 for a gallon of regular unleaded, 5 percent higher than in February. AAA spokesman Avery Ash said in the motor club's monthly report the national average could reach as high as $3.75 per gallon, though $3.65 for April is more likely.  The spring peak is within sight, he said, but prices may continue to climb through the month.  The average price for the last full week of March 2013 was $3.74 and $3.59 for the end of April.

Parts of California saw the highest national price for a gallon of regular unleaded with $4.12 per gallon. Great Falls, Mont., had the lowest average price of $3.18. For the year, EIA said it expects a national average of $3.45 for a gallon of regular unleaded and $3.37 in 2015.