President George W. Bush Wednesday called for US greenhouse gas emissions to be curtailed from 2025, but was roundly accused of doing too little, too late to combat climate change.

Seven years after abandoning the Kyoto treaty on global warming, Bush said the United States had shown it was serious about reducing growth in carbon dioxide and other planet-heating gases.

"Today, I am announcing a new national goal: to stop the growth of US greenhouse gas emissions by 2025," he said in a speech, which was short on specifics to attain that goal.

Bush said to reach the 2025 goal, "we will need to more rapidly slow the growth of power-sector greenhouse gas emissions so that they peak within 10 to 15 years, and decline thereafter."

The president did not detail any mandates to bring down industrial emissions, and warned Congress against passing new legislation that might "impose tremendous costs on our economy and American families."

Bush instead extolled the promise of new technology to clean up gas emissions, older technology like nuclear power and "clean coal," and a target to make US vehicles more fuel efficient.

Critics noted that the Bush proposal would allow the United States to keep raising its emissions until 2025, at a time when major powers are debating a post-Kyoto deal and scientists are warning that delay could be disastrous.

The president rebuffed clamours for urgent action not just from Congress, US states and big companies, but from all three of the contenders vying to succeed him -- Democrats Hillary Clinton and Barack Obama, and Republican John McCain.

"The Bush administration has spent most of the last eight years censoring scientists, pretending that global warming is a problem that doesn't exist, and standing in the way of solutions," Clinton said in a statement.

"Now that the administration has been forced to acknowledge global warming as a problem, they have put forward a proposal that looks like it was written by (Vice President) Dick Cheney's energy task force," she said.

The president's address came as 16 economies that together account for 80 percent of global greenhouse gas emissions gathered in Paris for the "Major Economies Meeting," the third in a series launched last September by Bush.

In Paris, South African environment minister Marthinus van Schalkwyk said Bush's new plan marked a retreat from his own previous modest goals, and would leave the United States "alone against the overwhelming majority of the world."

"It seems as if the current US administration wants to turn back the clock to where we were before the breakthrough achieved in Bali in December 2007," he said, referring to a UN plan aimed at replacing the Kyoto framework.

Kyoto's binding commitments expire in 2012. The president, who came belatedly to the climate change cause, is accused of trying to ram through a diluted regime that would focus on voluntary action rather than mandatory cuts.

Bush said efforts by 17 US states including California to use existing legislation, such as the Clean Air Act, to clean up their greenhouse gas emissions would have "crippling effects on our entire economy."

California's Republican governor, former movie star Arnold Schwarzenegger, commended Bush's admission that climate change presents a threat but said: "We must not let our emissions ever hit 2025 levels.

"I am glad that we all recognize the very serious threat in front of us -- what we need now is the sense of urgency to match that threat," he said in a statement that was echoed by environmental groups including the Sierra Club.

But Bush, having rejected Kyoto for its failure to apply binding gas targets on fast-growing China and India, said the United States would not take unilateral action that imperils US industry and jobs.

The United States supports a post-Kyoto regime that encompasses every major economy "and gives none a free ride," he said.

Nancy Pelosi, the Democratic Speaker of the House of Representatives, observed that Bush's speech came shortly after he welcomed Pope Benedict XVI to the White House.

Joining in the attacks on Bush's proposal, she recalled the pontiff's call last year for a "strong commitment to reverse those (environmental) trends that risk
making the situation of decay irreversible."