President George W. Bush intends to address a September 27-28 gathering of 16 nations in Washington on how best to combat global warming, which he now accepts to be a "serious challenge."

But while Europe and the scientific community push for new binding targets to reduce greenhouse gases, Bush's approach emphasizes technological change and voluntary action by governments and companies.

"Countries are not just eager but desperate for US engagement on this issue," said Elliot Diringer, director of international strategies at the Pew Center on Global Climate Change.

"But some are quite skeptical and want to make sure that the US initiative does not undermine the broader effort to launch formal negotiations in Bali," he said, looking ahead to a major conference in December.

The Washington gathering will follow an unprecedented summit of about 80 world leaders on Monday to debate climate change ahead of next week's annual General Assembly of the United Nations in New York.

Then in three months, the conference on the Indonesian island of Bali will look at what kind of greenhouse gas regime should succeed the Kyoto treaty, whose binding reductions on emissions expire in 2012.

Bush refused to adopt the "fatally flawed" Kyoto pact, arguing that it would cripple the US economy and that it placed no requirements on fast-developing nations such as China to cut their own greenhouse gases.

After taking office in 2001, the president said the science of global warming was still open to doubt, querying to what extent it was a man-made or natural phenomenon.

But in February, the Bush administration saluted the conclusions of UN scientists who warned that rising temperatures from fossil fuel pollution would worsen floods, droughts and hurricanes, melt polar sea ice and damage the climate system for a thousand years to come.

What remains in question is the administration's commitment to craft a tough successor to Kyoto that would encompass the United States, the world's biggest polluter, along with China and the other emerging industrial powers.

This month's Washington meeting will gather nations that together account for 90 percent of all greenhouse gas output, including Australia, Brazil, China, India, Japan, Russia and European powers.

The White House's Council on Environmental Quality said it hoped to feed the results of the Washington conference into a new global agreement by 2009 that establishes national plans to reduce gases such as carbon dioxide.

"These national strategies will be based on what is best for the individual country," council spokeswoman Kristen Hellmer said.

Bush is under pressure to take firmer action from a diverse collection of interests ranging from big business and the Democratic-led Congress through to evangelical Christians and a resurgent green lobby.

The Oscar-winning success of former vice president Al Gore's documentary on global warming, "An Inconvenient Truth," has helped to propel the debate onto America's front pages.

In the absence of federal action, several US states including the economic behemoth of California now have their own policies to reduce emissions and set up a European-style "cap and trade" market among corporate sectors.

Several bills have appeared since the Democrats retook control of Congress last November, including a market-based proposal from veteran senators Joseph Lieberman and John Warner that they say would still safeguard the US economy.

However, some suspect Bush of pursuing a public-relations exercise on climate change as the clock winds down on his presidency.

National Environmental Trust president Phil Clapp said the sort of voluntary regime favored by Bush had been discredited in the 1990s.

"The president is recycling a 15-year-old approach on global warming that was invented by his father's administration and trying to call it new," he said.

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