The US nuclear security summit is a step towards a safer world but ensuring fissile materials stay out of the hands of rogue non-state actors remains the key challenge, analysts say.
US President Barack Obama hailed an agreement by the 47-nation summit to a four-year deadline to lock down loose nuclear materials to prevent them from falling into militant hands.
Obama said the world was littered with poorly guarded fissile material and that a nuclear-armed militant group could threaten global "catastrophe".
Several countries including Ukraine, Mexico and Canada also declared their intention to give up highly enriched uranium but experts were divided on whether it was an "epoch-making" event or simply a "public-relations exercise".
The Obama administration "can justifiably pat itself on the back", said Paul Stares, Director of the Center for Preventive Action, part of the New York-based think-tank the Council on Foreign Relations.
"Important progress was made on a critical issue: increasing the security of nuclear material stored around the world from theft by terrorist groups and criminal gangs," he wrote on the CFR website.
"The Obama administration has put itself in a much stronger position to argue for increased international pressure against North Korea and Iran, not to mention other potential proliferators, to relinquish their nuclear ambitions," he added.
The summit was also hailed by observers in Japan – the only country to have been attacked with atomic bombs, and a neighbour of nuclear-armed North Korea.
"It's epoch-making that leaders from as many as 47 countries made the agreement" to lock down loose nuclear material, said Isao Itabashi, an anti-terrorism expert at Tokyo think-tank the Council for Public Policy.
"The threats existed since long before the 9/11 attacks but are still out there," said Itabashi, although he stressed it would be difficult to shut off militants' access to radioactive materials completely.
"We have seen some incidents in Japan in which these materials were stolen or slipped out of control," he said, referring to a researcher who stole radioactive material from his lab and scattered it at a train station in 2000.
"There are many countries which have a looser watch," he said, pointing out that radioactive materials are used in hospitals, laboratories and industry.
But other observers played down the gains from the meeting.
John Harrison, a security analyst at Singapore's S Rajaratnam School of International Studies, called the meeting a "public relations exercise that achieved nothing practical".
"It begs the question, what was this summit all about" asked Harrison, manager of terrorism research at the graduate school's International Centre for Political Violence and Terrorism Research. "It was a pointless summit."
Robert Dujarric, who runs Temple University's Institute of Contemporary Asian Studies in Tokyo, said the summit was a political victory for Obama, who "acted presidential and showed a mix of leadership and consensus-building".
"The real gains: very marginal, at best," he added in an e-mail.
The focus on "nuclear terrorism shows US voters Obama isn't soft on America's enemies but is pretty meaningless since by definition those who might be interested in this type of weapon, Al Qaeda [and others] weren't at the summit."
Looking ahead to the 2012 meeting in South Korea, Baek Seung-Joo, of the state-run Korea Institute for Defence Analyses, said it should help "garner more international support for its [South Korea's] drive to denuclearise the peninsula".
"The summit will not provide a fundamental solution to North Korea as its nuclear programme is in a different category," Baek said.
"However, North Korea will face further pressure to abandon nuclear weapons."
The Washington Post praised Obama for his focus on securing nuclear material, but also noted the difficulty of eliciting "more co-operation from prickly foreign governments" to reach the goal.
Neither did the summit "do much about several of the world's most pressing proliferation problems, including Iran's drive for a nuclear bomb and North Korea's refusal even to negotiate about its arsenal", said the newspaper.
The Wall Street Journal noted that leaders at the summit "stepped back from legally binding plans" to secure vulnerable nuclear material. (AFP)