Obama in push for 'world without nuclear weapons'

US president Barack Obama yesterday said that he is pushing for "a world without nuclear weapons" and is committed to deterring nuclear proliferation, ahead of a two-day 53-nation nuclear summit in Seoul.

"The danger of nuclear terrorism remains one of the greatest threats to global security. That is why in Seoul we need to keep at it," he said before the summit focussing on reducing nuclear access by terror groups to radioactive material and build a nuclear bomb.

Obama also assured that the United States can further reduce its nuclear weapons stockpile while maintaining its strategic deterrent and international commitments.

He also pledged to work with Russia and China, speaking ahead of a summit in Seoul aimed at reducing the risk of nuclear terrorism.

Obama emphasised the US's unique position to seek change but said "serious sustained global effort" was needed.

The meeting is being attended by representatives from some 50 countries.

Speaking to students at Hankuk University, Obama reiterated the commitment of the US as ''the only nation to have ever used nuclear weapons'' to reducing its nuclear arms stockpile.

He also spoke, he said, as a father who did not want to see his daughters growing up in a world with nuclear threats, a comment which drew applause from his student audience.

He also addressed North Korea's nuclear ambitions directly in his speech, saying that the US has ''no hostile intent'' towards the country, but ''there will be no rewards for provocation''.

He warned Pyongyang that its planned long-range missile launch would only increase its isolation.

Pyongyang says it is preparing to launch a long-range missile which it says will put a satellite in orbit.

''You can continue with the road you are on but we know where that leads,'' he said, addressing the North Korean leaders directly.

''Today, we say: Pyongyang, have the courage to pursue peace.''

Earlier, he and South Korean President Lee Myung-bak said North Korea risked further sanctions and isolation if it did not cancel its launch plans.

The launch will contravene an agreement Pyongyang reached last month which would have seen it receive food aid in exchange for a partial freeze on nuclear activities and an end to ballistics tests.

The North also agreed to allow UN inspectors in, the US said.

The invitation comes three months after Kim Jong-un came to power following the death of his father, Kim Jong-il.

The North said the launch - between 12 and 16 April - would mark the 100th birthday of former leader Kim Il-sung.

Obama echoed similar sentiments towards Iran.

"There is time to solve this diplomatically. It is always my preference to solve these issues diplomatically," he said.

"Iran's leaders must understand that there is no escaping the choice before it. Iran must act with the seriousness and sense of urgency that this moment demands," Obama said. "Iran must meet its obligations."

Iran insists there is no military element to its programme but Western powers fear it is constructing nuclear weapons.