you are the light of the world

US President Barack Obama has called on world leaders to come together at the UN climate summit in Copenhagen as time runs out to strike a deal. President Obama told delegates the international community's ability to take collective action was in doubt. Leaders have gathered for the final day of the summit amid uncertainty over the shape of any eventual deal.

A draft political agreement drawn up by a small group of countries was rejected during overnight discussions. Addressing the summit on Friday, President Obama said, while the science of climate change is not in doubt, I think our ability to take collective action is in doubt right now, and it hangs in the balance. He said he had come to Copenhagen "not to talk, but to act".

Unchecked, he said, climate change would pose unacceptable risks to international security, the world economy and the planet.