EU leaders are set to argue over their own contributions at their next regular summit at the end of October.

The high-level EU and G20 meetings come in the countdown to a critical UN summit in Copenhagen, which is intended to seal a new global deal on fighting climate change.

EU officials say that it will only be possible to reach a deal if the US, 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 halt the growth of their own soaring greenhouse gas emissions.

The EU is therefore keen to bring the two sides together 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.

A week ago, the commission said that European taxpayers should pay from two billion to 15 billion euros towards the global fight against climate change, 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, Japan 4.4 billion euros, China 7.9 billion euros and India two billion euros.