Key points: terrorism, nonproliferation

WASHINGTON — President Obama's nuclear summit of 47 world leaders met two goals as it ended Tuesday: reaching international consensus on the need to keep weapons-grade nuclear materials out of the hands of terrorists, and re-establishing U.S. leadership on nonproliferation.

Several nations agreed to dispose of weapons-grade uranium, end plutonium production, tighten port security and other voluntary steps. All participants endorsed Obama's call to secure vulnerable nuclear materials within four years, and agreed to seek further cooperation even as they stopped short of any enforceable international agreement.

"We have seized this opportunity," Obama said in a news conference closing the summit. As a result, he said, "the American people will be safer, and the world will be more secure."

Obama conceded that when it comes to enforcement, "we're relying on goodwill."

The unanimous communique expressed support for security agreements "that will not infringe upon the rights of States to develop and utilize nuclear energy for peaceful purposes and technology." Representatives of participating countries plan to reconvene in December for an update. Another leaders' summit is planned for 2012 in South Korea.

The gathering provided Obama an opportunity to recast how other nations see the U.S. on nuclear issues, in contrast to the Bush administration, whose strategy had included developing new nuclear weapons and expanding circumstances under which they could be used.

It also was a chance for Obama to show U.S. voters another side of him. The public's impression of him could improve if they view him as effectively exerting leadership on the world stage. The summit featured imagery of Obama surrounded by nearly four dozen other world leaders at the largest international conference since the World War II era, and produced results.

China said it will work with the U.S. and Europeans on new U.N. sanctions against Iran for its nuclear program. Last week Obama signed a new U.S.-Russia arms reduction treaty.

Gary Samore, the arms control and nonproliferation coordinator for the National Security Council, said of all the agreements: "We used the summit shamelessly as a forcing event to ask countries to bring house gifts. Almost every country came with something new."

"This event has some political dimension to it above and beyond the actual content," said Leonard Spector, the deputy director of the James Martin Center for Nonproliferation Studies. "There's a solidarity, a recognition this is a problem we all confront and we should do our best."

More than 2,000 tons of plutonium and highly enriched uranium for civilian and military use are in dozens of countries, summit documents said, with 18 documented cases of theft or disappearance.

Obama said Tuesday that an apple-size amount of plutonium in the hands of terrorists could kill or injure hundreds of thousands of people. "Terrorist networks such as al-Qaida have tried to acquire the material for a nuclear weapon, and if they ever succeeded, they would surely use it," Obama told participants Tuesday. "Were they to do so, it would be a catastrophe for the world."

A 'cruel irony'

The president described "a cruel irony of history" two decades after the Cold War, in which "the risk of a nuclear confrontation between nations has gone down, but the risk of nuclear attack has gone up."

The nation of Georgia disclosed that Georgian authorities last month prevented an attempt by a criminal gang to smuggle highly enriched uranium.

The summit produced a number of concrete agreements, including a decision by Ukraine to dispose of all of its estimated 90 kilograms of highly enriched uranium by 2012, and an accord under which the U.S. and Canada will help Mexico convert a research reactor to lower enriched fuel. Chile also has said it is giving up highly enriched uranium.

Russia announced at the summit that it will shut down its last plutonium production reactor.

The U.S. and Russia signed on Tuesday a long-awaited agreement under which the former Cold War rivals each will dispose of 34 metric tons of weapons-grade plutonium and seek to get rid of additional material.

"The initial combined amount, 68 metric tons, represents enough material for approximately 17,000 nuclear weapons," said a joint announcement of the agreement signed by Secretary of State Hillary Clinton and Russian Foreign Minister Sergei Lavrov. "Both countries aim to begin actual disposition by 2018, after the necessary facilities are completed and operating."

Russian President Dmitry Medvedev called the nuclear summit "a complete success."