The United States won't budge, despite intense pressure to change its stance on climate change and the Kyoto Protocol.

As the United Nations climate conference moved into its final phase in Montreal Wednesday, world leaders urged Washington to join global efforts to combat global warming.

But U.S. Undersecretary of State Paula Dobriansky said, even though Washington now accepts the phenomenon is real, it won't even agree to talk about international co-operation under the UN Framework Convention on Climate Change (UNFCC).

"It is our belief that progress cannot be made through these formalized discussions," Dobriansky told reporters at a news conference.

"We believe that the best approach, and the best way forward, is one that takes into account diversified approaches and differing opinions. One size does not fit all."

Under the Kyoto Protocol -- adopted by 146 countries in 1997 -- signatories are committed to reducing their greenhouse gas emissions more than 5 per cent by 2012.

The U.S. has formally withdrawn from the landmark treaty, which it argues could harm development and economic growth, insisting that other negotiations and voluntary investment in new emissions-curbing technologies can reverse the problem.

Critics of the White House stand argue, however, that the Kyoto targets can never be met without the cooperation of the United States -- simply because it currently accounts for 25 per cent of emissions linked to climate change.

Scientists blame carbon dioxide, for example, and five other heat-trapping gases for rising global temperatures and disrupted weather patterns.

A devastating report released Tuesday revealed that 2005 was in fact the worst year for extreme weather -- with the hottest temperatures, most Arctic melting, worst Atlantic hurricane season and warmest Caribbean waters.

It's also been the driest year in decades in the Amazon, where a drought may surpass anything in the past century, said the report released by the World Wildlife Fund at the UN conference Tuesday.

According to the chief scientist for WWF's Climate Change Program, Lara Hansen, cyclical patterns alone cannot explain the number of hurricanes this year.

"What we're seeing now is even beyond what that cyclical nature would lead us to believe has happened," she told The Associated Press.

Meanwhile, a leading U.S. climate scientist is warning that the world has just 10 years to act on climate change.

Dr. James Hansen told the American Geophysical Union in San Francisco that a rise of just 1 degree Celsius in temperature would take the Earth into climate patterns it has not seen for at least 500,000 years.

Reduction in greenhouse gases can only be achieved with determined action on energy efficiency, Hansen said.

Going far beyond the Kyoto Protocol participants, the Montreal summit has attracted more than 8,000 delegates from 185 countries. Despite its opposition to Kyoto, the U.S. is in attendance as a member of the UNFCC.

Looking ahead to Kyoto's 2012 expiration date, officials at the summit due to end Friday are focused on whether countries will be able to agree on continued efforts beyond then.

"There is an urgent need to send a signal to the world about the future," the conference chair, Canadian Environment Minister Stephane Dion said, signalling his eagerness to kickstart a wider discussion of future commitments.

Scientists say, unless the world cleans up its act significantly in the coming decades, it won't be able to avoid an irreversible environmental catastrophe.

Prime Minister Paul Martin told the conference Wednesday that changes already occurring in the Canadian North proved that urgent action is needed much sooner.

"The time is past to debate the impact of climate change. We no longer need to ask people to imagine its effects, for now we can see them," he said.

Echoing the Liberal leader's remarks, members of the Inuit Circumpolar Conference lodged a complaint before the Inter-American Commission on Human Rights on Wednesday.

"Because climate change is threatening the lives, health, culture and livelihoods of the Inuit, it is the responsibility of the United States, as the largest source of greenhouse gases, to take immediate and effective action to protect the rights of the Inuit," the complaint said, alleging that U.S. environmental policy was having an effect tantamount to cultural genocide.

In her comments to reporters, Dobriansky said she had not seen the complaint and could not, therefore, comment on it.

Established under the authority of the Organization of American States, the human rights commission does not have binding powers.