The Sting star, who is a vocal environmental activist, addressed representatives from 193 countries at the U.N. headquarters as well as the U.N. Secretary-General Ban Ki-moon.

Redford urged leaders to realise the time for "climate denial" is over and insisted the world must move away from using fossil fuels if it is to avoid catastrophe.

He said, "Now an increase of just two degrees Celsius is all that separates our planet from being less habitable. Unless we move quickly from fossil fuels, we're going to destroy the air we breathe, the water we drink, the health of our children, grandchildren and future generations. And if we're going to avoid the worst of the impacts then we just got to act boldly. We've all got to do more.

"We must be a movement that involves every single nation on Earth because climate change affects every nation on Earth. This is our only planet, our only life source. This may be our last chance. Our planet's resources are limited, but there's no limit to the human imagination and our capacity to solve bigger problems."

Other stars to discuss global issues at the United Nations include Leonardo DiCaprio, Daniel Craig and Victoria Beckham.

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Daily Mail: 'Save the world before it's too late:' Robert Redford addresses UN ...