The US Congress must pass a "strong" climate change bill before the global warming summit in Copenhagen this December if it is to have a chance of persuading China and India to sign up to a new treaty, says Bill Clinton.

Democrats in the US House of Representatives are expected to announce a compromise move on Wednesday that would give the go-ahead to a bill to tackle global warming. Success would beat expectations in a political climate increasingly hostile to cap-and-trade.

Voters in Indiana last week asked Barack Obama what his highest priorities would be in his "first 1,000 days in office". Ahead of universal healthcare and ending the Iraq war, the first item on Mr Obama's list was comprehensive energy reform.

Observers of the increasingly commuter-focused presidential debate in the US could be forgiven for thinking that the pain of high petrol prices has driven the issue of global warming off the political agenda.

Barack Obama and John McCain on Monday stepped up their increasingly tetchy exchange over high petrol prices, with Mr Obama accusing his rival of being in the "pocket of big oil' and Mr McCain accusing his opponent of hypocrisy.

Mr Obama, whose opinion poll numbers have slid sharply since his trip to Europe and the Middle East last month, on Monday unveiled a "comprehensive energy plan' that promised to wean the US off foreign oil while providing short-term relief to consumers.