Obama calls for nuclear arsenal reduction

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".

"As president I will seek reductions in the US and Russia's tactical weapons while rejecting the nuclear weaponisation that North Korea and Iran may be seeking," he said. 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.

But a senior Russian official said that the US deployment of anti-missile shields was a huge hurdle to any further cuts in the nuclear arsenals of the former Cold War foes.

"How can we take the idea of strategic nuclear weapons reductions seriously when the United States is building up its ability to intercept these ... weapons?" Deputy Prime Minister Dmitry Rogozin said.

The Kremlin also said that the new cuts in nuclear stockpiles should expand beyond Russia and the US and include other nuclear armed states.

Earlier in the day, President Obama and German Chancellor Angela Merkel discussed the importance of Europe's relationship with the US.

"Sometimes there has been talk that the trans-atlantic alliance is fading in importance, that the United States has turned its attention more towards Asia and the Pacific," Obama said.

"In conversations with Chancellor Merkel and earlier with your president, I reminded them that from our perspective the relationship with Europe remains the cornerstone for our freedom and our security."

Merkel was also keen to emphasise the impact the US had on Germany's own history.

"When the president addresses the crowd in front of the Brandenburg Gate, he will be a president who can do this in front of a gate that is open," she said.

"Other presidents had to remind us all that the wall needed to be torn down, and the wall is down and this is what we owe to our American partners and friends."

Obama spoke in front of Brandenburg Gate nearly 50 years after former US President John F Kennedy's famous Cold War speech in this once-divided city.

The US president made several references to the history of the gate, and the city, during his speech, which was warmly recieved by the cheering crowds.

"Today's threats are not as stark as they were half a century ago, but the struggle for freedom and security and human dignity, that struggle goes on,'' he said.

"I come here to this city of hope because the test of our time demands the same fighting spirit that defined Berlin a half-century ago. 

"No wall can stand against the yearnings of justice, yearnings of freedom, yearnings of peace that stand in the human heart."

Obama acknowledged the need for more action on climate change, saying Germany and Europe had led the way, while the US still needed to do more.

He also addressed the recent national Security Agency scandal, saying that the spy programmes "confront real dangers", while acknowledging that the government needed to address concerns regarding privacy versus security.

"This is what makes us different to those on the other side of the wall," he said.