US president Barack Obama has outlined a major new initiative against nuclear weapons.
President Obama offered to host a global summit on nuclear security within a year, as part of a drive to stop the production of materials that can be used in nuclear weapons.
He Obama delivered his message in a speech at Prague Castle at the EU-US summit.
President Obama has surprised many observers with the speed at which he is moving to address the issues of nuclear weapons proliferation, particularly the fear that terrorist groups like Al-Qaeda might acquire the technology for an atomic bomb.
He said the US will take concrete steps to create a world without nuclear missiles.
'The United States will take concrete steps towards a world without nuclear weapons,' he said.
He confirmed that the US would maintain a safe and effective arsenal to deter any adversary, but will begin reducing its arsenal.
He said the thousands of nuclear weapons are the most dangerous Cold War legacy.
President Obama also offered to host the global conference on nuclear security, as the Obama administration views the spread of nuclear weapons material as its top security concern.
The launch of a long-range ballistic missile by North Korea was condemned by the White House as a violation of UN Security Council resolutions and as a provocative act.
President Obama called on North Korea to abandon its pursuit of weapons of mass destruction if it is to be accepted into the international community.
He said: 'I call on North Korea to honour its commitment to abandon all nuclear weapons programmes.'
He added that North Korea had broken the rules and must be forced to change. North Korea said the step was intended purely to launch a satellite.
On the issue of a missile defence shield, Mr Obama said the US will continue with its plans as long as a potential nuclear threat persists from Iran.
He said: 'If the Iranian threat is eliminated, we will have a stronger basis for security, and the driving force for missile construction in Europe will be removed.'
Mr Obama also said the US is ready to take a leading role in tackling climate change.
'In this global effort, the US is now ready to lead,' he said of the fight against climate change and ending dependence on fossil fuels.
President Obama then joined EU leaders, including Taoiseach Brian Cowen, for a lunchtime meeting that concentrated on efforts to combat climate change.
