US President Barack Obama says Washington is ready to lead the way in ridding the world of nuclear weapons but will push ahead with plans for a missile defence shield in Europe.His speech came just hours after the firing of a rocket by North Korea. He told a huge crowd in central Prague that “the United States will take concrete steps towards a world without nuclear weapons to put an end to cold war thinking, we will reduce the role of nuclear weapons in our national security strategy and urge others to do the same. Make no mistake, as long as these weapons exist, the United States will maintain a safe, secure and effective arsenal to deter any adversary and guarantee that defence to our allies including the Czech Republic”. The former eastern bloc country is one of the sites for the planned missile defence system. He paid tribute to the country for its transition to democracy. “Sametová revoluce – the Velvet Revolution taught us many things and it proved that moral leadership is more powerful than any weapon… that’s why I am speaking to you in the centre of a Europe that is peaceful, united and free, because ordinary people believed that divisions could be bridged”, he said. The rousing address capped a week in which EU-US relations were under the spotlight over a range of potentially divisive issues.