Environmentalists have long urged a substantial increase in the fuel-economy standards, which they view as one of the most effective means of reducing the US appetite for foreign oil.

Each manufacturers' fleet of passenger cars must average 27.5 miles per gallon.

However, US automakers have warned that higher fuel standards might compromise safety because vehicles would probably have to be lighter. Transportation Secretary Norman Mineta echoed a similar view in a letter to congressional leaders requesting formal authority to reform the Corporate Average Fuel Economy (CAFE) standard for cars.

Some Democrats and some auto industry sources believe the administration already has the authority to raise CAFE standards and doesn't need congressional action.

Bush likened higher gasoline prices to a tax as he stopped at a fueling station after touring hurricane-hit Biloxi, Mississippi.

He said that the Republican-led Congress was weighing some ideas to ease the pain at the pump, including legislation on the fuel standards.

"I encourage them to give me that authority," Bush said. "It's authority that I use for light trucks. And I intend to use it wisely if Congress would give me that authority."

The administration in March raised fuel standards for popular-selling light trucks, including sport utility vehicles, pickups and minivans.

POLITICAL IMPACT

Gasoline prices, which have vaulted above US$3 a gallon and are increasingly pinching consumers budget, are a key concern for Bush, whose approval ratings have been mired in the low to mid-30 percent range.

Bush, in an interview with "NBC Nightly News," said the low poll ratings were partly due to high gasoline prices.

"There is a strong economy, and yet there is a certain unease," Bush said. "I think some of it has to do with gasoline prices," he said, also citing uncertainty in the Middle East due to Iraq and Iran.

"I've been up in the polls, and I've been down in the polls, but I'm going to continue to do what I think is right for the country," Bush told NBC.

His Republican allies worry gasoline prices could put their dominance in Congress at risk in November's midterm elections.

Bush rolled out some initiatives earlier this week such as ordering a probe into price gouging and suspending additions to the US emergency stockpile of oil.

Democrats say Bush's plan falls short and called for measures including suspending the 18 cent per-gallon gasoline tax and eliminating industry tax credits.

Senate Republicans weighed in on Thursday with ideas like giving taxpayers a US$100 check and opening an Alaskan wildlife refuge to oil drilling. They also called for suspending a retail fuel tax.

In March, the Bush administration announced it would raise fuel economy standards by 1.9 miles per gallon for sport utility vehicles, pickups and vans -- the biggest gas guzzlers -- between 2008 and 2011.

The change for light trucks featured a restructuring of how fuel standards are calculated for the class, something Mineta said in his letter to House and Senate leaders would also be crucial for passenger cars to maintain safety.

General Motors Corp. said in a statement it would work with the administration. "As changes are made, we want to be sure this program is designed in the fairest way possible for all auto manufacturers," company spokeswoman Sherrie Childers Arb said.

Some environmental and consumer advocates have urged that mileage standards go up significantly since many passenger cars, especially foreign-made vehicles, far exceed the current standard.