He said that 189-nation talks in Nairobi should seek ways to widen the UN-led fight against global warming to all nations, including the United States, after a first period of the Kyoto Protocol runs out in 2012.

"It's essential that the United States is part of a global agreement to binding global carbon reductions," he said as he toured the muddy Kibera slum, where a million people cram into tiny homes made of corrugated iron, mud or wood.

"I can't think of a greater legacy for the last two years of the Bush presidency than to work on a bipartisan basis with Democrats as well as Republicans" for a deal to cut emissions, he said.

He declined to say whether he reckoned it was more likely that the United States would join a long-term fight against climate change after the Democrats won control of Congress in elections last week.

Bush pulled out of Kyoto in 2001, saying that its caps on emissions of greenhouse gases, mainly from burning fossil fuels, would cost US jobs and that the scheme wrongly excluded developing nations from the goals for 2012.

HEATWAVES, FLOODS

Kyoto binds 35 industrialised nations to cut emissions of greenhouse gases to 5 percent below 1990 levels by 2008-12 as a first step to slow rising temperatures that could spur heatwaves, floods, rising sea levels and a spread of disease.

"A tonne of carbon dioxide emitted in Boston is as dangerous as a tonne emitted in Nairobi ... and there are many more tonnes emitted in Boston," Miliband said.

He said the world should agree by 2009 on ways to extend the Kyoto Protocol. Nairobi is unlikely, however, to set any deadlines.

Miliband toured schools, walked past open sewers running through the slum, inspected water pipes and stalls selling charcoal, bananas or beans. Many young Swahili-speaking children, showing off their English, chanted "how are you!"

Few in the slum had heard that Britain made aid to Africa and combating climate change the main goals of its presidency of the Group of Eight industrial nations last year.

"Life here is not easy," said John Kyalo, 21, sitting by the roadside. "I'm good at laying tiles but I have no work. Things have not got better in recent years."