After weeks of upwardly creeping prices, the $4 gallon of gasoline finally arrived in the Philadelphia area yesterday.

What's more, some local stations now are charging more for customers who pay by credit card than they do for motorists paying cash.

Seven gas stations in the eight-county area posted prices of $4 or more for regular-grade yesterday, according to AAA Mid-Atlantic. All were on the Pennsylvania side of the Delaware River - two in Philadelphia, three in Conshohocken, and one each in Doylestown and Morrisville.

"It seems like it's been inching up every day, even if it's just by a penny or two," Catherine L. Rossi of AAA MidAtlantic said.

"We had expected that some stations in the Philadelphia area would reach $4. We're hopeful that the average price would not top $4, though it is certainly possible," she said.

Yesterday's average for Philadelphia and the four suburban counties in Pennsylvania was $3.83 a gallon, up a penny from Sunday, AAA said. In the three suburban South Jersey counties, the average yesterday was $3.66, also up 1 cent from Sunday.

In South Jersey, the highest price recorded by AAA yesterday was $3.97 a gallon at a station in Voorhees.

"Crude [oil] is the driving force" for the gasoline price hikes," Rossi said. "It really depends on what happens with crude. If it goes down or stays the same, we may not reach $4. If crude goes up, it surely will."

Light, sweet crude for June delivery jumped 76 cents yesterday to settle at a record $127.05 a barrel on the New York Mercantile Exchange.

AAA Mid-Atlantic, which surveys stations in the eight- county Philadelphia area daily, has noticed a trend developing as gasoline prices soar.

"Some stations are charging more for credit card use," Rossi said. "They're passing on the card-processing fees to drivers." Credit card transactions generally run about 6 cents more a gallon than cash, she said.

Nationally, Americans were paying an average of $3.79 for a gallon of regular gasoline yesterday, unchanged from Sunday, according to a survey by AAA and the Oil Price Information Service.

Diesel, used to transport a wide range of goods, now costs a nationwide average of $4.52 a gallon at the pump. Those prices are likely to keep rising, after crude's upward track.

Yesterday's diesel average was 69 percent higher than the $2.68 a gallon at the start of 2007, according to AAA.

Drivers in some parts of the country are paying considerably more than the average for gasoline. Gasoline pump prices in parts of California have been stuck above $4 a gallon for weeks now, although the statewide average is down to $3.96. Prices in Alaska and Connecticut are averaging just above $4 a gallon.

The national average was $3.18 a gallon a year ago.

Oil prices were boosted yesterday by a report that the Organization of Petroleum Exporting Countries would not increase production before its next meeting Sept. 9.

The announcement came days after Saudi Arabia's oil minister said the kingdom, the world's largest oil producer, had increased production 300,000 barrels a day earlier this month.

Although the response in the trading pits to that move was tepid, the modest increase should nonetheless help grease a tight global market, said John Felmy, chief economist for the American Petroleum Institute, the industry's leading U.S. trade group.

"Certainly seeing increased production is helpful in terms of increased supplies," he said.