June 27 -- Gasoline prices have fallen almost 7 cents in the past two weeks in the second dip in prices this year, an industry analyst said Sunday.

The weighted national average price for all three grades of gasoline fell 6.6 cents to $1.97 per gallon Friday after rising more than 59 cents from mid-December to June, said analyst Trilby Lundberg, who publishes the semimonthly Lundberg Survey. The survey regularly polls nearly 8,000 service stations across the nation.

The biggest selling gas, self-serve regular, averaged $1.94 a gallon.

Lundberg said the recent price drop, which followed another decline two weeks ago, stemmed partly from the moderation of oil prices and to the completion of U.S. refinery maintenance projects undertaken to prepare for summer gasoline demand.

Falling crude oil prices were also a factor. At the New York Mercantile Exchange, crude oil futures set for August delivery ended trading at $37.55 a barrel Friday, down from $38.45 a barrel two weeks earlier. Crude oil prices had been more than $40 a barrel in previous weeks.

OPEC's decision to increase oil production in July might bring down oil prices further, but fears of terrorism and sabotage in Iraq and Saudi Arabia may contribute to another oil price surge, she said.

OPEC, which supplies more than a third of the world's crude oil, announced earlier this month it would raise its official daily production quota by more than 2 million barrels to 26 million barrels and, if necessary, by an additional 500,000 barrels on Aug. 1.

The national weighted average price of a gallon of gasoline at self-serve pumps on Friday, including taxes, was about $2.04 for mid-grade and $2.13 for premium.

The most expensive gas in the country was in San Francisco, where regular unleaded sold for $2.27 a gallon. The cheapest was in Tulsa, where gas was $1.69.