The European Union (EU) has challenged rising powers India and China to brake their soaring greenhouse gas emissions in return for Western financial support.
"We need to make a credible financial commitment to the developing world. The equation is straightforward: no money, no deal, but if there are no actions, no money," European Commission President Jose Manuel Barroso said at an informal EU summit in Brussels on Thursday.
Next week, the leaders of the Group of 20 (G20) nations are set to meet in Pittsburgh, Pennsylvania, with international funding for the fight against climate change high on the agenda.
According to estimates from the commission, the EU's executive, it will cost around 100 billion euros ($147 billion) per year by 2020 to fight climate change in developing countries.
Thursday's informal EU meeting echoed that estimate and a further call for quick-start money of 5 billion to 7 billion euros in aid to poorer countries per year up to 2012.
But in a clear challenge to rising powers such as Brazil, China, India, Mexico and South Africa, EU leaders stated that "this estimate presupposes appropriate mitigating actions by developing countries, especially those that are economically more advanced".
Moreover, "all countries, except the least developed", should help pay the world's poorest states to fight climate change, the EU summit statement said.
That is a clear tightening of early drafts of the document, which only called for "ambitious mitigation reductions" around the world, without singling out any state or region.
The high-level EU and G20 meetings come in the countdown to a critical United Nations summit in Copenhagen, which is intended to seal a new global deal on fighting climate change.
EU leaders on Thursday were at pains to point out the urgency of finding a deal in December.
"The climate is changing much faster than expected. ... This underlines the urgent need to reach a global, ambitious and comprehensive agreement in Copenhagen," the joint statement said.
"The world has a fever: we need to stop the acting and start the action," said Swedish Prime Minister Fredrik Reinfeldt, whose country currently holds the EU's rotating presidency.
With just 80 days to go until the Copenhagen summit, there are 2,500 negotiating points that world powers still have to agree, said Reinfeldt, who will represent the EU in the Danish capital.
EU officials say that it will only be possible to reach a deal if the United States, historically the world's largest polluter, agrees to legally binding greenhouse-gas emission targets.
But US leaders have long maintained that they will only agree to such caps if the major developing powers pledge to brake the growth of their own soaring greenhouse-gas emissions.
The EU is therefore keen to bring the two sides by proposing a "global key", which would define rich and poor nations' responsibilities and calculate how much money each country should pay to the worldwide fight against climate change.
"You cannot move forward unless the world moves together. We have to bring in not just the old G8 (group of the world's leading developed economies): this involves all the countries of the world," British Prime Minister Gordon Brown said.
A week ago, the commission said that European taxpayers should pay from 2 billion to 15 billion euros per year toward the global fight against climate change by 2020, depending on whether the bill is calculated according to the EU's current wealth or greenhouse gas emissions.
Using the same formulae, the US would pay up to 12.6 billion euros per year, Japan 4.4 billion euros, China 7.9 billion euros and India 2 billion euros.