NEW YORK (CNN/Money) - Gasoline prices at the pump posted a sixth straight weekly decline last week, but don't expect them to keep falling.

Experts say weaker crude prices, higher demand and lower inventories are likely to keep gasoline prices from dropping this summer. At least one analyst predicts that prices might even rise again.

The latest pump price slipped to an average of $1.56 per gallon, a drop of 1.7 cents from a week ago, the Energy Department's Energy Information Administration reported Monday.

The price of a gallon of gasoline, based on a weekly survey of more than 800 service stations by the EIA, has fallen 17 cents a gallon from its record high reached in March right before the war in Iraq, but Dave Costello, economist at the EIA, said the prices will likely level as the summer driving season heats up.

"Crude oil costs, gasoline inventories and demand are three key factors contributing to gasoline prices," he added.

Crude oil prices, which account for about 45 percent of the cost of gasoline, have fallen significantly due to the quick resolution of the war in Iraq, and that price drop has already been passed on to motorists at the pump, Costello explained.

Prices of crude have reached their lowest levels in over five months after OPEC said last week it will cut back less than expected on the extra crude it pumped to cover supply during the war in Iraq.

Costello said the higher OPEC output, however, will just fill out currently low national motor gasoline stocks, which are estimated at 201 million barrels, about 3 percent below the 5-year average.

In addition, the travel industry could see a strong rebound this summer, said Geoff Sundstrom, spokesman at AAA, the nation's largest club for motorists. He suggested that there is a strong pent-up summer driving demand.

"We believe that people have been putting off vacations due to concerns about terrorism, the war and the economy. Now the war, at least, is largely behind us" Sundstrom said. "With that in mind, we think the demand for gasoline should be reasonably high."

The EIA estimated the summer gasoline demand will average at 9.18 million barrels per day, up 1.6 percent from last summer. The growth in demand is also driven by gradual acceleration of the U.S. economy out of the 2001-2002, according to the EIA.

Costello predicted that consumers will continue to enjoy some price relief at the pump for a few more weeks. However, he said the gradual decline will eventually even out.

Related story • Gasoline taxes on the rise • Gas prices state-by-state

"We don't also see prices turning higher this summer, unless there's some kind of domestic disruptions," he predicted.

OPEC's decision to boost production quotas will be the one force holding down increases in gasoline prices, Costello added.

"Retail gasoline prices will probably go down another dime or so," he said. However, they will not go below last summer's low of $1.47, he added.

"It will probably hover around $1.50 a gallon, and remain pretty flat for the summer," Costello said. "But I can see the prices dip below $1.50 by late September."

John Kilduff, an energy analyst at Fimat USA, a global commodities brokerage, felt that the current tight gasoline supply would cause prices to rise. "We are at levels that in the past several years had caused gasoline prices to approach the $1.70-type national average record levels."

If the price spike does come, it will be in the next four to six weeks, he said.