The departure from office of US president George W. Bush will bring a much brighter outlook to international talks on global warming and the $64bn market in greenhouse gas emissions, said the United Nations' top official on climate change.

"The US is very promising. All three [presidential] candidates are interested in climate change, all three want international engagement, all three favour a cap-and-trade approach [on emissions], which augurs well for the continuation of the carbon market," said Yvo de Boer, executive secretary of the UN Framework Convention on Climate Change, the parent treaty to the Kyoto protocol, in an interview with the Financial Times.