US President Barack Obama says the risk of nuclear attack has increased, calling it a "cruel irony" after the end of the Cold War.
In an opening address to the first full day of the Nuclear Security Summit - 47 countries wrestling with ways to keep bomb materials out of the hands of terrorists - the president notes the risks of nations going to war with nuclear weapons had decreased.
Nevertheless, Obama says, "the risk of a nuclear attack has gone up." He is speaking of the threat of terrorists getting their hands on nuclear materials.
Obama's remarks were advance excerpts of his speech released Tuesday by the White House.
China's agreement to work with the US on possible sanctions against Iran and Ukraine's decision to get rid of highly enriched uranium put some wind in Obama's sails as he presses global leaders to join him in locking down all nuclear materials within four years.
Obama's meeting with Chinese President Hu Jintao was the last of the summit warm-up sessions before the US leader sat down with his guests at a working dinner Monday night.
After the Hu meeting, White House national security aide Jeff Bader said Iran was a major topic of discussion at the 90-minute session.
The upbeat assessment reflected a recent warming of US-Chinese diplomatic ties. Still, the meeting produced no breakthroughs. And Chinese spokesman Ma Zhaoxu did not mention sanctions in a statement on Hu's meeting with Obama.
In Beijing on Tuesday, Chinese Foreign Ministry spokeswoman Jiang Yu said: "China always believes that dialogue and negotiation are the best way out for the issue. Pressure and sanctions cannot fundamentally solve it."
But she added that China supports a "dual-track strategy," combining diplomacy with the possibility of international sanctions against Iran.
In Tehran on Tuesday, Iran expressed doubts that China would back the US push for new sanctions. Foreign Ministry spokesman Ramin Mehmanparast said he did not think Hu was signaling that with his comments.
The US already has the robust backing of Great Britain, France and Germany in adopting further sanctions against Iran. Russia, too, has shown a willingness to join the sanctions effort, meaning the required clean sweep of permanent members the United Nations Security Council.
Brazil and Turkey, which both hold non-permanent seats on the UN Security Council, are studying an alternative proposal to deal with Iran's controversial nuclear program, Brazilian Foreign Minister Celso Amorim said Monday.
While the United States worries about Iran's nuclear program, Turkey has its own concerns about Israel's nuclear program. Israeli Prime Minister Benjamin Netanyahu opted not to attend Obama's summit, and insiders said he had expected Turkey and Egypt to use the conference as a platform to challenge him over his country's widely assumed nuclear arsenal, which the Jewish state never has acknowledged.
Iran's UN Ambassador Mohammad Khazee on Monday declared Obama's new nuclear policy, which excludes Iran from a US pledge not to use nuclear weapons against countries that do not have them, an act of "state terrorism" because it threatens nations with weapons of mass destruction.
Meanwhile, the Ukrainians, who gave a major boost to arms control in 1994 when they agreed to surrender the nuclear weapons they inherited in the collapse of the Soviet Union, agreed to get rid of their weapons-grade fuel by 2012.
The focus of the summit is tons of plutonium and highly enriched uranium are believed to be insufficiently protected from international criminal gangs and terrorist organizations.
The officials at the summit are expected to sign a joint declaration to guide future work toward locking away and cleansing the globe of materials still too easily accessible to terrorists.