US President Barack Obama laid out an ambitious plan to rid the world of atomic weapons in Prague Sunday, evoking his successful election campaign slogan of 'Yes we Can' to call for world action to face up to the nuclear threat.
With his message sharpened after communist North Korea launched a rocket only hours before, Obama warned in his speech to thousands of people in the historic heart of Prague that the threat of a nuclear attack had increased.
"The threat of global nuclear war has gone down but the risk of nuclear attack has gone up," said Obama, saying the testing of nuclear weapons had risen and the technology of building a bomb had spread as a result increasing the risk of nuclear weapons falling into the hands of terrorists.
Following last week's agreement with Russia for new talks on nuclear arms, Obama proposed a series a steps to eventually eliminate existing nuclear arsenals.
This included halting the proliferation of nuclear weapons to additional states and "a lock down" on the material used in manufacturing atomic weapons.
He also said that the future of the US's planned controversial missile defence system in Central Europe depended on Iran.
If Iran committed itself to a peaceful nuclear programme, then the missile defence system which is planned to be located in Central Europe and has resulted in strains in US-Russia relations, would be abandoned, Obama said.
"The existence of thousands of nuclear weapons is the most dangerous legacy of the Cold War," said Obama. "The world must stand together to stop the spread of these weapons."
The US president went on to roundly condemn North Korea, saying Pyongyang "broke the rules by testing a rocket that could be used for long range missiles".
"Rules must be binding, violations must be punished," he told the tens of thousands of people gathered to hear his speech in front of the gates leading to the Prague castle.
Pyongyang had said it was putting a communications satellite into orbit, but Japan, South Korea and Washington believe the launch was a screen to test a ballistic missile.
Obama's keynote speech on nuclear non-proliferation in Prague was a highlight of his five-nation trip, which marks his first major foray onto the world stage since becoming president in January.
The US leader also argued for a strengthening of the nuclear Non-Proliferation Treaty through boosting the resources and authority for stronger international inspections around the world.
He also wants to ensure that there are real and immediate consequences for countries that break the rules, such as automatic referral to the UN Security Council.
The president is also to meet European Union (EU) leaders Sunday in Prague as part of an EU-US summit before flying to Turkey later in the day.
The US-EU meeting is expected to focus on climate change and economic relations. The Czech Republic is hosting the summit as it holds EU's sixth-month rotating presidency until June 30.
Obama and his wife Michelle arrived in Prague on Saturday after attending a summit in France and Germany marking the 60th anniversary of the security organisation NATO and a two-day meeting in London of the Group of 20 world's big economic powers.
The US leader's speech in Prague comes as Central European nations mark the 20th anniversary of the fall of communism and he praised the action taking by the Czech people in changing their political destiny.
Prague's 1989 Velvet Revolution had "helped to bring down a nuclear power without a shot being fired", Obama said.