European Union leaders were on Wednesday told they have to find 15 billion euros a year to help developing countries fight global warming if this week's summit is to be deemed successful.

Leaders from the EU's 27 member countries are split into three camps going into a summit starting Thursday at which they will try to agree a common line to take into United Nations negotiations in Copenhagen starting on December 7.

Britain is among those who are willing to commit to funding, while a wait and see bloc is headed by Germany -- and eastern European nations with Poland at their head only want to help "based on their means," according to diplomats.

"There are two questions up for discussion: the amount of money and burden-sharing," said a European Commission source who asked to remain anonymous.

"Success would be agreement to come up with 15 billion euros (22.5 billion dollars) per year from 2013 to 2020 and 1.5 billion euros per year between 2010 and 2013," for so-called 'fast-start' funding in the period leading up to a replacement for the existing global climate deal, the official said.

London believes 100 billion euros will be required each year, of which it says the EU should commit between eight and 10 billion annually -- although that figure could fall if it helps secure a concrete commitment at the summit.

The European Commission -- the bloc's executive body -- estimates that poorer countries would need around 100 billion euros (149 billion dollars) annually from 2020 to fight global warming.

A draft document laying out the EU's common position on this key issue is at the moment full of blank spaces where figures should be.