Environment ministers from around the world are trying to break a deadlock over climate change policy, at a major UN conference in Montreal.
Environmental activists have called for action on global warming
Ministers want to agree a deal to tackle global warming that includes the US and developing nations.
Some countries are refusing to limit their greenhouse gas emissions after the Kyoto Protocol expires in 2012.
"There is an urgent need to send a signal to the world about the future," conference chairman Stephane Dion said.
The US never ratified the Kyoto treaty. It says it is serious on climate change, but is still resisting targets and is instead pursuing a policy of voluntary reductions through use of new technology.
Along with many developing nations, its fears its implementation of the Kyoto Protocol could harm development and economic growth.
Mr Dion, Canada's environment minister, has proposed a wider discussion of what various countries might be prepared to do after 2012.
This would run alongside negotiations on new, more stringent carbon reduction targets for industrialised nations.
The response appears to have been generally positive, with China and Australia - which rejected the Kyoto limits - said to be among those supporting the move.
But India, some of the major oil producing nations and the US - the world's largest carbon emitter - do not seem to have been won over, says the BBC's Elizabeth Blunt in Montreal.
Canadian Prime Minister Paul Martin said environmental changes to Canada's north proved that urgent action was needed.
"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.
In a video address to delegates, French President Jacques Chirac said climate change was "a brutal and urgent reality, the most serious threat weighing on the future of humanity".
Meanwhile, a leading US climate scientist has warned that the world has just one decade to get to grips with climate change.
Dr James Hansen told a meeting of American Geophysical Union in San Francisco that just 1C more of warming would take the Earth into climate patterns it has not experienced for more than 500,000 years.
But determined action on energy efficiency to bring about reductions in greenhouse gas emission could lead to some stabilisation, he said.