WASHINGTON — President Barack Obama urged global leaders Friday not to be complacent in the face of an evolving threat from terrorists who he said are eager to unleash a devastating nuclear attack. "It would change our world," he declared.
Hosting his last nuclear security summit, Obama said the world has measurably reduced the risk of nuclear terrorism by taking "concrete, tangible steps." He said no terrorists have thus far obtained nuclear material, and he praised recent moves by Argentina, Switzerland and Uzbekistan to eliminate their stockpiles of highly enriched uranium.
Still, Obama said, the prospect of the Islamic State group or other extremists getting a weapon remains "one of the greatest threats to global security." He pointed out that the IS group had already used chemical weapons and that al-Qaida has long sought nuclear material.
"There is no doubt that if these madmen ever got their hands on a nuclear bomb or nuclear material, they would certainly use it to kill as many people as possible," Obama said.
For the dozens of world leaders assembled in Washington this week, the harrowing risk of nuclear terrorism has been front and center, alongside concerns about North Korea's nuclear weapons program. Yet Obama worked to open the summit's final day on an optimistic note, hailing the nuclear agreement with Iran as a "substantial success" and a model for future diplomacy.
Obama sought to use the controversial Iran agreement as an argument for his carrot-and-stick approach to deterring nuclear proliferation as he huddled with other U.N. Security Council members who negotiated the deal along with the U.S. He credited Iran with taking steps to meet its commitments and touted the importance of other countries taking reciprocal steps.
"It will take time for Iran to reintegrate in the global economy, but Iran is already beginning to see the benefits of this deal," Obama said.
Critics of the deal, both in Congress and other world capitals, have fumed about sanctions relief and other benefits Iran is receiving, concerns that grew this week after U.S. officials told The Associated Press that the Obama administration is considering easing the ban on U.S. dollars being used in transactions with Iran. House Speaker Paul Ryan has called that prospect "deeply disturbing."
Obama acknowledged that the Iran deal hasn't swept away other issues the U.S. and other nations still have with Iran; support for terrorism and Tehran's ballistic missile program typically top that list. Still, he said all the nations that negotiated the deal could agree that it's been an effective way to address the narrower issue of nuclear proliferation in Iran.
"This is a success of diplomacy that hopefully we will be able to copy in the future," Obama said.
Leaders came to the nuclear summit with commitments in hand, known in diplomatic-speak as "gift baskets," to strengthen nuclear security. The White House spelled them out in a blizzard of fact sheets released on the summit's closing day.
Latin America and the Caribbean are now free of highly enriched uranium, the White House said, praising Argentina by name for converting its remaining stockpile of the potential bomb-making material into a less dangerous form. The U.S. and Japan also pledged to remove highly enriched uranium from a Japanese research reactor to reduce the risk of theft and nuclear terrorism.
The United States, in newly declassified statistics, said its own national inventory of highly enriched uranium has dropped from 741 metric tons two decades ago to 586 metric tons as of 2013. Fissile materials like highly enriched uranium and separated plutonium are necessary ingredients to make nuclear bombs.
Still, frustration over the slow pace of reducing nuclear stockpiles shadowed the summit, Obama's last major push on denuclearization. The absence of key players — especially Russia — further underscored the lack of unanimity confronting global efforts to deter nuclear attacks.
After six years of prodding by Obama and others before him, the global stockpile of fissile material that could be used in nuclear bombs remains in the thousands of metric tons. What's more, security officials warn that the radioactive ingredients for a "dirty bomb" are alarmingly insecure in many parts of the globe.
Ahead of the summit, fewer than half of the countries participating had agreed to secure their sources of radiological material, readily available in hospital, industrial and academic settings. Concerns about substances like cesium or cobalt getting in the wrong hands have escalated sharply following deadly attacks by IS, raising the disturbing prospect of a nuclear attack on a Western city.
As the summit opened Thursday, leaders trained their focus on North Korea, whose continued provocations have stoked concerns throughout the region. Obama discussed steps to deter further North Korean missile tests during a meeting with Chinese President Xi Jinping. In another session with the leaders of Japan and South Korea, he called for vigorous implementation of stepped-up U.N. sanctions.
President Vladimir Putin of Russia, whose massive nuclear weapons stockpile is rivaled only by the U.S., declined to attend this year's summit. Moscow scoffed at what it deemed U.S. efforts to control the process and take power away from international agencies. Prime Minister Nawaz Sharif of Pakistan, another nuclear-armed country, canceled his trip following a bombing that killed 72.
Associated Press writers Bradley Klapper, Matthew Lee and Matthew Pennington contributed to this report.