By Tom Doggett

WASHINGTON, April 23 (Reuters) - After rising for 12 weeks in a row, U.S. retail gasoline prices finally fell to give drivers a little bit of a break at the pump, the government said on Monday.

The national price for regular unleaded gasoline dropped a slight 0.7 cent to $2.87 a gallon, 4.5 cents cheaper than a year ago, according to the federal Energy Information Administration's weekly survey of 800 service stations.

It was the first time since Jan. 22 that the average weekly gasoline price had declined, but consumers won't see much change in their fill-up costs.

The much larger Lundberg survey of 7,000 stations showed that gasoline jumped 8.4 cents over the past two weeks to $2.87 a gallon.

The AAA travel group's daily survey of 85,000 service stations reported the average gasoline price fell to $2.85 a gallon on Monday.

More U.S. oil refineries are coming back online after routine maintenance and unplanned outages, increasing gasoline production levels and putting less upward pressure on price.

However, the savings at the pump could be short-lived. The U.S. price of oil, which accounts for about half the cost of making gasoline, soared nearly 3 percent on Monday at the New York Mercantile Exchange on fears of more disruptions in Nigeria's oil production in response to that country's disputed presidential election this weekend.

In the EIA's new weekly survey, West Coast service stations had the most expensive fuel by region, up 2.3 cents at $3.22 a gallon. Among major cities, San Francisco had the highest gasoline costs at $3.40 a gallon, up 1.5 cents.

The best regional price was along the Gulf Coast at $2.76 a gallon, down 0.8 cent. Houston had the lowest city pump price at $2.75 a gallon, up 1.8 cents.

The EIA also reported that gasoline prices were up 0.8 cent at $3.29 in Los Angeles, up 4.9 cents at $3.14 in Seattle, up 0.6 cent at $2.95 in Miami, down 4.1 cents at $2.93 in Chicago, up 0.7 cent at $2.86 in New York City, and up 1.9 cents at $2.78 in Denver.

Separately, the price of diesel fuel fell 2.6 cents to $2.85 a gallon, the first decline in a month and 2.5 cents lower from a year ago.

The West Coast had the most expensive diesel, down 0.3 cent to $2.95 a gallon. Diesel was cheapest along the Gulf Coast states, down 3.4 cents to $2.82 a gallon.

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