For the first time in history all of the major -– the world's major economies have come together to accept their responsibility to take action to confront the threat of climate change, Obama said.

"After extremely difficult and complex negotiations this important breakthrough lays the foundation for international action in the years to come," Obama said in his first public statement on his return from Copenhagen.

This progress did not come easily and we know that progress on this particular aspect of climate change negotiations is not enough, he said referring to the Copenhagen accord reached by the US and BASIC countries in the final hour of the summit.

"Going forward we're going to have to build on the momentum that we established in Copenhagen to ensure that international action to significantly reduce emissions is sustained and sufficient over time."