ATLANTA (CNN) - Gasoline prices shed about 3 cents per gallon over the past three weeks, according to a survey published Sunday.

The Lundberg survey found the average price of self-serve regular was $2.30 per gallon on Feb. 10, down from about $2.33 on Jan. 20.

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"This is a lull," said publisher Trilby Lundberg. But, she said, "prices are not likely to fall much more, if at all," in the coming weeks.

News about some major OPEC nations -- particularly Iran and Nigeria -- are triggering concerns about the future of oil prices, she said.

"Iran has been the chief disturbing element among traders looking at potential risk to the supply of oil." Iranian leaders have threatened to manipulate world oil prices if the U.N. Security Council imposes sanctions amid the international dispute over Iran's nuclear activities.

Also, oil facilities in Nigeria have been struck by a string of violence and robberies in recent months.

Lundberg said U.S. demand for gasoline is on the rise, since January is "the lowest baseline consumption month" -- the time Americans drive the least.

"So even if crude oil prices did not rebound, I believe we can expect higher gasoline prices rather than a continued slide."

The slight price decline over the past three weeks followed seven weeks of rising prices at the pump. The Jan. 20 survey marked a 20-cent hike from two weeks earlier.

Lundberg said the massive snowstorm this weekend in the northeast is unlikely to impact gasoline prices. There is already "more than efficient heating oil supply," she said, so all the natural gas being used to heat homes probably will not be strong enough to have much of an effect on crude oil prices.

The survey published Sunday found the lowest cost of gasoline was in Portland, Ore., where a gallon of self-serve regular cost $2.07; the highest was in Honolulu at $2.78.

Some other prices:

--Denver, $2.17

--Cleveland, $2.19

--Atlanta, $2.20

--Houston, $2.23

--Phoenix, $2.37

--Sacramento, $2.41

--Hartford, Conn. $2.42

--Baltimore, $2.33

--Anchorage $2.30

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