The national average U.S. retail price of diesel fuel dipped a bit to $1.717 from the previous average of $1.718, the Department of Energy reported May 3.

Once again, the highest prices in the nation were in California, where the average cost of diesel rose from $2.247 last week to $2.274 this week. Truckers in that state have protested the steady increases at rail yards, interstates and at ports.

Fuel prices were also high in New England, at $1.754; in the Rocky Mountain region, at $1.892; the Central Atlantic region, at $1.742; and on the West Coast, where the average price is $2.146.

Other prices included the Lower Atlantic region, where the average price is $1.605; the Midwest, at $1.657; the Gulf Coast, at $1.627; and the East Coast, at $1.653.

Meanwhile, OPEC is mulling whether to increase its target price for a barrel of oil, the group's president, Purnomo Yusgiantoro, has said.

The organization currently tries to keep the oil price between $22 and $28 per barrel. But OPEC has complained the value of oil sales has been hit by the slump in the dollar.

Any rise is likely to raise concerns about the effect of higher fuel and raw material costs on global growth.

Earlier this year, the United States criticized plans by OPEC to cut output as a tax on consumers and warned that it may derail a fragile economic recovery.

OPEC accounts for about 40 percent of world oil production.