EXETER, Feb 1: Britain appealed to the United States on Tuesday to sign up to climate-saving cuts in greenhouse gas emissions as environmentalists warned of approaching Armageddon.

Opening a three-day scientific meeting to assess the threat of global warming, environment minister Margaret Beckett said it was vital Washington become more involved.

"A significant impact is already inevitable - we need to act now to limit the scale of warming in the future and avoid even worse effects," she said. "We would like America to engage more fully with these discussions about where we might go in the future."

America is one of the largest emitters of greenhouse gases like carbon dioxide (CO2), but rejects what is now majority scientific opinion that mankind is largely to blame for climate warming and has refused to join the Kyoto Protocol on curbing emissions.

Kyoto, which comes into force on Feb 16, aims to cut CO2 emissions by developed states by 5.2 per cent below 1990 levels by 2008-12. US President George Bush is seeking a less stringent target.

Washington's aim is to cut the amount of greenhouse gas emissions for every dollar of economic output by 18 per cent in 2012 compared to 2002. The economy is likely to grow at a faster pace, meaning overall emissions will rise.

Ms Beckett, who said there was no doubt human activity contributed to climate warming, added there was no hope of persuading Bush to sign up to Kyoto. What was imperative was to persuade the American administration and public to examine what to do after 2012.

"I don't suggest that America will now join the Kyoto protocol," she said. "But clearly it would have much more impact if we are able to re-engage America in considering what we can do in the longer term."

EXTREME WEATHER: Ms Beckett said extreme weather events like droughts and floods were expected to become more frequent and worse, noting that the world had just experienced the 10 hottest years on record.