Obama pledges reduction in nuclear stockpiles

US President Barack Obama has renewed his call to reduce the world's nuclear stockpiles during a speech in front of Berlin's iconic Brandenburg Gate.
Obama pledged on Wednesday to reduce the number of nuclear weapons held by Russia and the US by one-third during a speech which used the theme "peace through justice".
He also called for a global reduction in the manufacturing of materials used in the construction of nuclear weapons.
The speech also included pledges over tackling climate change, which the president called "the global threat of our time" and unemployment.
Al Jazeera's Nick Spicer reports from Berlin.