Host Canada and the European Union reckon they can allay US fears that any discussions would inevitably lead to binding targets, opposed by Washington, which has pulled out of the UN's Kyoto Protocol on curbing global warming.

"This would be the start of discussions ... that do not mean commitments to a future course," a senior Canadian official said. "We think the United States could find a way to join such discussions."

"We believe that it's possible to come up with a process, a dialogue that has something of interest for everybody," echoed Sarah Hendry, head of the British delegation which holds the European Union's rotating presidency.

Washington bluntly told the conference on Monday that it was not interested in discussing new commitments, saying it was focusing on domestic measures to brake a rise in emissions and investing heavily in clean technologies like hydrogen.

Still, Canada and the European Union hope the Montreal talks will launch a twin track - new talks among Kyoto nations about what to do beyond 2012 and a wider set of discussions also involving developing countries and the United States.

Kyoto, by contrast, requires about 40 developed nations to cut emissions of heat-trapping gases by 5.2 percent below 1990 levels by 2008-2012. President George W. Bush pulled out in 2001, branding Kyoto an economic straitjacket.

Environmentalists said many nations were lowering expectations about any big steps to combat global warming, widely blamed on emissions from burning fossil fuels in power plants, factories and cars. The 10 hottest years since records began in the 1860s have been since 1990.

"If that's all that comes out of here then it's not enough," said Steve Sawyer, climate policy director at Greenpeace, of hopes for vague discussions on what many environmentalists call the biggest long-term threat to life on the planet.

UN reports say the buildup of greenhouse gases may cause catastrophic climate shifts with more powerful storms, droughts and floods. Icecaps could melt, raising sea levels and drowning coastal cities and low-lying Pacific islands.

A paper submitted by a group of 77 developing nations and China urged rich nations to consider new commitments for cutting greenhouse gases beyond 2012 and aim to complete their negotiations in 2008. It did not mention any commitments by developing nations.