The administration of US President George W. Bush has long rejected the role of human activity on the phenomenon, even as experts estimate that one quarter of the heat-trapping pollutants in the atmosphere come from US sources.

However, a steady stream of pressure from international experts, public opinion, the new Democratic majority in Congress and even the Supreme Court has chipped away at that stance.

In early April, the United States acknowledged the alarming diagnosis of global warming and its potential disastrous consequences after the release of a report by the Intergovernmental Panel on Climate Change (IPCC), the United Nations's top authority on global warming which meets this week in Bangkok to discuss measures to take in response.

Bush, criticized around the world for his refusal in 2001 to ratify the Kyoto Protocol aimed at reducing greenhouse-gas emissions, saying it would hurt the US economy, now says he takes global warming "very seriously."

But he has not accepted any measures other than incentives, particularly ones that favor biofuels, to fight it.

In Congress, former US vice president-turned-environment crusader Al Gore has received a warm welcome. Hearings on the subject have increased and a draft law aimed at combating the phenomenon is up for debate this summer.

However, lawmakers remain uncertain how to tackle the matter.

Even though the United States is responsible for 25 percent of the world's greenhouse gases, only some states like California have taken initiatives to reduce pollution.

Bush refuses to consider any measure that could harm the growth of the US economy or threaten jobs. He reasons that economic prosperity is the only sure way to be able to address the consequences of global warming and finance the development of cleaner technologies, which tend to be more costly.

His administration also believes that any domestic initiatives will be useless as long as China, the world's second-biggest polluter, and India are not also forced to limit emissions.

But the US public is increasingly eager for some movement on global warming, even if it means denting economic growth or forcing automakers to downsize their vehicles in a land where sports-utility vehicles and big cars reign, a recent poll suggested.

Fifty-two percent of respondents in a New York Times/CBS News poll published Friday said the environment should come first, compared with 36 percent who said the economy should.

Ninety-two percent said they would agree with regulations that would require automakers to make more fuel-efficient cars, but few wanted cuts to affect them directly -- just 20 percent were in favor of a gasoline tax aimed at limiting consumption.

A report released in mid-April by a panel of retired US admirals and generals framed the issue in a different way, arguing that global climate change presented a serious national security threat.

The study described climate change as a potential "threat multiplier" in already fragile regions of the world, exacerbating impoverished and corrupt conditions that lead to failed states, "the breeding grounds for extremism and terrorism," and further straining US military resources.

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