"Time is not on our side and frankly we've just got to get on with it," Benn told Reuters on the margins of a two-day meeting in Berlin of environment and energy ministers from the group of 20 (G20) nations.

"I think there is a recognition that we absolutely have to launch the process at Bali. It's been encouraging in that sense," he said of the meeting's progress.

But success is far from guaranteed.

Kyoto took five years to negotiate and another eight to come into force -- a timeframe that, if repeated, scientists say would push the world deep into unknown climate territory.

Scientists say global average temperatures will rise by between 1.8 and 4 degrees Celsius this century unless urgent action is taken to curb emissions of so-called greenhouse gases from burning fossil fuels for power and transport.

But the world's top polluter the United States rejected Kyoto as economic suicide and has made repeated efforts to undermine it.

At the same time booming carbon emitters such as China and India are not bound by the treaty and are resisting calls for them to agree to binding cut targets under any successor deal.

Germany has said a new deal must be decided by the end of 2009 at the latest. But even that is very tight if ratification is to take place before 2012. "We've had some really straight talking over the past couple of days," was all Benn would say when asked if the end of 2009 deal deadline remained a possibility.

The United States has called a meeting of major emitter nations at the end of September -- a move welcomed by some as evidence President George W. Bush has finally got the climate message and rejected by others as a bid to undermine Bali.

Benn, who was appointed head of the Department of Environment, Food and Rural Affairs in June as part of Prime Minister Gordon Brown's new cabinet, emphasised that the Bali talks should be at the centre of climate negotiations.

"The British government really welcomes the fact that the United States is now engaged in this way because that does represent a change from before," Benn said.