Britain and France have announced that they will each contribute at least £1.5 billion to the climate change fund for 2010 to 2012 to help developing nations finance environmental schemes.
Speaking at a joint news conference with French president Nicolas Sarkozy, Gordon Brown said: "This world deal at Copenhagen must be ambitious, global, comprehensive [and] legally-binding within six months."
The British prime minister added that he was confident that Europe would pay its share of the £10 billion fund.
EU leaders are reportedly attempting to agree on a figure before any deal reached at the Copenhagen summit comes into force.
In related news, the chief negotiator of the China and G77 group of nations has called on the US president to dramatically increase America's level of assistance.
He stated that the amount of money set aside by the International Monetary Fund for global financial crises should be reapportioned to help with the climate change effort.