NEW YORK — With the price of gas above $3.50 a gallon in all but one state, there are signs that Americans are cutting back on driving, reversing a steady increase in demand for fuel as the economy improves.

Gas sales have fallen for five straight weeks, the first time that has happened since November, according to MasterCard SpendingPulse, which tracks spending at 140,000 service stations.

Before the decline, demand was increasing for two months. Some analysts had expected the trend to continue because the economic recovery is picking up.

“More people are going to work,” said John Gamel, director of gasoline research for MasterCard. “That means more people are driving and they should be buying more gas.”

Instead, about 70 percent of the nation’s major gas-station chains say sales have fallen, according to a March survey by the Oil Price Information Service. More than half reported a drop of 3 percent or more — the sharpest since the summer of 2008, when gas soared past $4 a gallon.

A gallon of unleaded regular costs $3.77 on average. Gas is already 41 cents more expensive then at this point in 2008, when it peaked at $4.11 in July.