Climate change is a top issue at the G8 meeting. The United States, the world's largest oil consumer and the biggest spewer of total carbon dioxide emissions that heat the atmosphere, is the only one of the countries at the summit not to have signed the Kyoto treaty to cut carbon dioxide emissions.

The United States is doing its part, administration officials say, pointing to over $20 billion in spending on climate change activities by the end of 2005.

That amount includes systems to monitor land and ocean conditions, as well as programs to wean US dependence on crude oil and get more energy from renewable sources like corn-based ethanol and wind and solar power.

The administration has proposed spending $1.7 billion to develop hydrogen-powered cars and the stations to fuel them, more than $2 billion on low-emission coal plants and $3.6 billion in tax incentives to spur use of wind, solar and other renewable energy sources.

Environmental groups said Bush is merely trying to repackage to an international audience an energy plan he pushed in the US Congress. "He's trying to sell the same horse twice here," said Dan Becker of the Sierra Club.

The administration's position that developing countries, particularly China, should turn to new energy sources is seen as hypocritical by some energy experts.

"(Bush) ought to take his own advice. I think it's a bit disingenuous," said Frank Verrastro, director of the energy program at the Center for Strategic and International Studies in Washington.

Environmental groups and US lawmakers have long called for sharply higher fuel mileage requirements on new vehicles as the only real way to rein in US oil consumption, reduce crude imports and slash tailpipe emissions.

Bush administration officials say they are acting to curb vehicle fuel usage, but they add market initiatives would work better than mandates to spur Detroit to produce cleaner cars.

"We have a multi-pronged strategy on fuel economy," Jim Connaughton, head of the White House Council on Environmental Quality, said, pointing to a $4,000 proposed tax credit for consumers to buy fuel-efficient vehicles like hybrids.

"We can't make progress faster than people's ability to purchase a new vehicle," Connaughton said.

After years of resistance from American automakers, the US Transportation Department raised the fuel economy standard for gas-guzzling SUVs and light trucks from 20.7 miles per gallon in 2004 to 21 mpg for the model year 2005, 21.6 mpg for 2006, and 22.2 mpg for 2007.

The department estimates the increase would save 3.6 billion gallons of gasoline over the 25-year life of the affected vehicles from the three model years. With one barrel holding 42 gallons, it means the fuel savings will average about 9,400 barrels per day during the 25-year period.

That amount barely stirs the surface of the current 20.9 million barrels of oil a day consumed by the United States.

"It's a drop in the bucket," Verrastro said.

US cars, trucks and buses account for 20 percent of US global warming pollution, as well as soot and smog that damage human lungs, according to the Natural Resources Defense Council, an environmental group.