The agreement was reached during all-night talks at the G8 summit in Japan.

Last year's G8 meeting had only agreed to "seriously consider" the cuts, but the heads of world's richest countries have now agreed to set a definitive target.

They say they will work with the almost 200 countries that have signed up to the UN Convention on Climate Change in order to achieve the goal.

Climate change has been one of the most problematic issues discussed by G8 leaders, who were divided over the scale of the targets they should set and whether developing countries should be required to also cut emissions.