SEOUL U.S. President Barack Obama vowed on Monday to pursue further nuclear arms cuts with Russia, urged China to follow suit and issued stern warnings to North Korea and Iran in their nuclear standoffs with the West.
Acknowledging the United States has more warheads than necessary, Obama held out the prospect of new reductions in the U.S. arsenal as he sought to rally world leaders for additional concrete steps against the threat of nuclear terrorism.
"We can already say with confidence that we have more nuclear weapons than we need," Obama told students at South Korea's Hankuk University a few hours before a global nuclear security summit opened in Seoul.
He pledged a new arms-control push with incoming Russian president Vladimir Putin when they meet in May. But any further reductions would face stiff election-year opposition from Republicans in Congress who already accuse him of weakening America's nuclear deterrent.
Obama laid out his latest strategy against the backdrop of nuclear defiance from North Korea and Iran, twin challenges that have clouded his overall nuclear agenda and the summit in Seoul.
He set expectations high in a 2009 speech in Prague when he declared it was time to seek "a world without nuclear weapons". He acknowledged at the time it was a long-term goal, but his high-flown oratory helped him win the Nobel Peace Prize.
In Seoul, Obama made clear that he was committed to that notion, saying "those who deride our vision, who say that ours is an impossible goal that will be forever out of reach", were wrong.
Though Obama was vague on exactly how such a vision would be achieved, he voiced confidence the United States and Russia, which reached a landmark arms-control treaty in 2010, "can continue to make progress and reduce our nuclear stockpiles".
"I firmly believe that we can ensure the security of the United States and our allies, maintain a strong deterrent against any threat, and still pursue further reductions in our nuclear arsenal," he said.
But another arms accord with Moscow will be a tough sell to U.S. conservatives who say Obama has not moved fast enough to modernize the U.S. strategic arsenal, a pledge he made in return for Republican votes that helped ratify the START treaty.
The United States and Russia are the two biggest nuclear powers, possessing thousands of warheads between them, arsenals that arms-control advocates say are capable of destroying the world several times over.
Obama said he wanted to take arms control talks with the Russians to a new level. "Going forward, we'll continue to seek discussions with Russia on a step we have never taken before - reducing not only our strategic nuclear warheads, but also tactical weapons and warheads in reserve," he said.
With U.S. officials privately expressing concern about China's opaqueness over its growing nuclear weapons program, Obama said he had urged the rising Asian power "to join us in a dialogue on nuclear issues, and that offer remains open".
NORTH KOREA, IRAN
Obama also used his speech to call on North Korea, which plans a long-range rocket launch next month, to curb its nuclear ambitions or face further international isolation.
"And know this - there will be no more rewards for provocations. Those days are over. This is the choice before you," he said, directing his comments at North Korea's leadership.
Chinese President Hu Jintao indicated to Obama during a one-on-one meeting on Monday that he took the North Korean nuclear standoff very seriously and was registering his concern with Pyongyang, a senior White House aide said.
China is the secretive North's only major ally.
"The two leaders agreed to coordinate closely in responding to this potential provocation ... and if necessary consider what steps need to be taken following a potential launch," the White House aide added, without elaborating on possible consequences.
Obama says the destitute North could be hit with tighter sanctions if it goes ahead with the rocket launch, but experts doubt China will back another U.N. Security Council resolution against North Korea.
The North says the rocket will send a satellite into space, but South Korea and the United States say it is a ballistic missile test.
Even though two previous launches of the long-range missile have failed, Washington says the North's missile program is progressing quickly and that the American mainland could come under threat within five years.
The flight path from a west coast launch pad will take the rocket south towards the Philippines. The Defense Ministry in Seoul said South Korea was drawing up a plan to shoot down any components that may crash into South Korean territory.
The ministry added that the main body of the rocket was being positioned into place for the launch.
Earlier on Monday, Obama accused Iran of having taken the "path of denial, deceit and deception" in the past but said there was still time for a diplomatic solution and that Iran had to act with a sense of urgency.
"Time is short," Obama said, referring to the prospects of renewed negotiations between Iran and world powers. "Iran's leaders must understand that there is no escaping the choice before it."
Iran says its nuclear program is purely peaceful, but Israel and Western nations believe it is moving towards a nuclear bomb that could change the regional balance of power.
Obama has urged Israel to hold off on any pre-emptive strikes on Iran's nuclear sites to give sanctions and diplomacy more time to work.
The U.S. president also met Russia's outgoing leader, Dmitry Medvedev, on the sidelines of the summit, with missile defense in Europe, Iran and the conflict in Syria topping their agenda.
Medvedev said he supported peace envoy Kofi Annan's mission to end fighting in Syria. Russia and China have shielded Syrian President Bashar al-Assad from U.N. Security Council condemnation by vetoing two resolutions over the bloodshed.
"We together with the U.S. president maintain that (Annan's mission) is a good way to reach at least an initial point of settlement and open the road for communication between various groups of society in Syria," he said.
(Additional reporting by Alexei Anishchuk, Yoo Choonsik, Jack Kim and Alister Bull; Editing by Nick Macfie and Robert Birsel)