WASHINGTON -- As world leaders opened a two-day nuclear security summit, President Barack Obama on Thursday urged closer security ties among the chief allies in Asia and increased cooperation with China to discourage North Korea from further advances in nuclear weapons.
Obama first met with Japanese Prime Minister Shinzo Abe and South Korean President Park Geun-hye. Together, they warned that Pyongyang would face even tougher sanctions and more isolation if it provokes again with nuclear and missile tests.
Later, Obama met Chinese President Xi Jinping, and both called for North Korea to give up its nuclear weapons. China also agreed to implement in full the latest economic restrictions imposed by the United Nations Security Council against Pyongyang.
More than 50 governments and international organizations are attending the summit on preventing nuclear terrorism -- the last in a series of global meetings where Obama has championed the issue. The risk posed by the Islamic State extremist group tops this year's agenda, but concerns about North Korea also are commanding attention.
"Of great importance to both of us is North Korea's pursuit of nuclear weapons, which threatens the security and stability of the region. President Xi and I are both committed to the denuclearization of the Korean Peninsula," Obama said at the start of his meeting with Xi.
"China and the U.S. have a responsibility to work together," Xi said in his comments made to reporters through an interpreter. As for their "disputes and disagreements," the Chinese leader said the two sides could "seek active solutions through dialogue and consultation."
North Korea announced its fourth nuclear test in January, followed by a space launch in February. The moves have heralded more convergence among often-fractious powers in East Asia -- at least on the need to press the government of Kim Jong Un toward disarmament.
Japan and South Korea have compelling reasons to get along. They both host U.S. forces and are both within range of North Korean missiles. But their relations have been strained by differences that date back to Japan's colonial occupation of Korea in the first half of the 20th century and its military's use of "comfort" women during World War II.
But those tensions have eased some. Abe said North Korea's nuclear and missile capability is a "direct and grave threat" to them all.
"Should it choose to undertake yet another provocation, it is certain to find itself facing even tougher sanctions and isolation," Park said of Pyongyang.
North Korea's Kim also has alienated the country's traditional benefactor and main trading partner, China. The U.S. has long urged China to take a more forceful role in pressing North Korea, and Chinese Vice Foreign Minister Zheng Zeguang said after Obama's meeting with Xi that the two sides agreed that the new U.N. resolution "should be implemented in full and in its entirety."
The U.S. and China also released joint statements vowing robust collaboration to improve nuclear security and to implement a global climate-change deal, and reported progress on the issue of cybersecurity.
But they were at odds in other areas.
According to Zheng, Xi told Obama that China is "firmly opposed" to the U.S. deploying a new missile defense system in South Korea, saying it was against China's national security interests and would affect the strategic balance in the region.
The U.S. and South Korea are considering such a deployment to counter the threat from North Korea. China contends that the system would also give the U.S. radar coverage over Chinese territory. Russia opposes it, as well.
The U.S. has also opposed China's move to build artificial islands and military facilities in the disputed South China Sea. Japan and South Korea are similarly concerned about China's military build-up and assertive actions in the region's disputed waters.
Xi told Obama that the South China Sea islands -- claimed by several other Asian governments -- have been China's territory since ancient times, and it has the right to defend its territorial sovereignty and maritime rights, Zhang said.
Separately, the White House announced that the United States and China would sign the Paris Agreement on climate change on April 22, the first day on which the United Nations accord will be opened for government signatures. Officials cast that as a statement of joint resolve by the world's two largest emitters of greenhouse gases.
"We, our two countries, with this joint statement, are taking an important step forward by encouraging the entry into force of this agreement," Brian Deese, Obama's senior climate-change adviser, told reporters.
The announcement was intended to spur other countries to sign the deal.
Enriched uranium
As concerns about terrorism in Europe rise in the wake of Islamic State-linked attacks in Paris and Brussels, Obama also met Thursday with French President Francois Hollande.
The nuclear security summit continues today with a special session focused on preventing the Islamic State and other extremists from obtaining nuclear materials and attacking urban areas.
On Thursday, the U.S. said a strengthened nuclear security agreement among nations was finally set to take force after ratification by a critical mass of countries. The stricter rules include new criminal penalties for smuggling nuclear material, and expanded requirements for securing materials and nuclear facilities worldwide, and are intended to reduce the likelihood of terrorists getting their hands on ingredients for a nuclear bomb.
On terrorism, Yukiya Amano, the head of the watchdog International Atomic Energy Agency, said in an interview Wednesday that the threat of groups such as the Islamic State obtaining nuclear materials is real.
In the past two decades, there have been about 2,700 reported instances of missing radioactive materials, including some involving highly enriched uranium.
"We never know if we know everything," Amano said. "This could be the tip of the iceberg. Some are illicit trafficking, very professional. Some people are trying to sell it. We have to think that the threat is real."
Amano said one potential safeguard will come with an amendment to the Convention on the Physical Protection of Nuclear Material, a 1987 treaty that stiffens standards for the physical protection of nuclear materials. The amendment requires countries to protect nuclear facilities and radioactive materials within their borders. Serbia and the Marshall Islands announced Wednesday that they would ratify it, and six more countries are needed for the amendment to take effect. Amano said he expected more to sign on in the "near future."
The United States says it's making progress in reducing its stockpiles of highly enriched uranium. The White House says it's declassifying and publicly releasing a national inventory of highly enriched uranium for the first time since 1996. As of late 2013, the U.S. had about 586 tons of highly enriched uranium. That's a drop from the 741 the U.S. had in 1996.
Fissile materials like highly enriched uranium and separated plutonium can be used to make nuclear bombs.
Notably absent from the summit is President Vladimir Putin of Russia, who is boycotting the meeting. The White House pointed out that Russia has nevertheless cooperated on nuclear matters, mentioning its role in the multiparty talks with Iran over curbing its nuclear program. Iran was not invited to attend the summit.
Deputy national security adviser Ben Rhodes, however, noted that the U.S. maintains "ongoing cooperation and dialogue with them on issues related to nuclear security, and that's important work that is ongoing."
But Russia is "going to miss out on an opportunity to coordinate with the rest of the international community on these important issues," Josh Earnest, the White House spokesman, told reporters Wednesday.
Information for this article was contributed by Matthew Pennington, Josh Lederman, Kevin Freking and Darlene Superville of The Associated Press; by Mark Landler, Coral Davenport and David E. Sanger of The New York Times; and by David Nakamura, Steven Mufson and Carol Morello of The Washington Post.
A Section on 04/01/2016