Developing nations have not been convinced that industrialised countries will fulfill pledges to help fund emissions cuts, which could hinder their economies.
Sarkozy also called for leaders in Copenhagen to agree on a deal that would be "legally binding within six months" and suggested a new target for a global reduction in deforestation.
Gordon Brown, the British prime minister, said any treaty agreed in the Danish capital must be consistent with a Group of 20 pledge to maintain global warming to a maximum of two degrees Celsius, compared to pre-industrial times.
Yvo de Boer, the UN climate chief, said the EU funding was a major boost to the
negotiations for a global climate deal in Copenhagen.
"One of the things that has been holding this process back is lack of clarity on how short-term financial support is going to be provided to developing countries," de Boer said.
"And the fact that Europe is going to put a figure on the table will, I think, be hugely encouraging to the process."
Environmental group Greenpeace gave the EU cash pledge a cautious welcome.
"Short term funding is necessary but there is a risk that this will be used to greenwash an outcome which is weak and doesn't have any structural needs-based funding. Climate change will not be beaten in three years," Joris den Blanken, the group's EU campaigner said.