SEOUL, South Korea (AP) - Material that can be used to make nuclear bombs is stored in scores of buildings spread across dozens of countries. If even a fraction of it fell into the hands of terrorists, it could be disastrous.
Nearly 60 world leaders who gathered Tuesday in Seoul for a nuclear security summit agreed to work on securing and accounting for all nuclear material by 2014. But widespread fear lingers about the safety of nuclear material in countries including former Soviet states, Pakistan, North Korea, Iran and India.
While the threat of nuclear terrorism is considered lower now than a decade ago, especially after the death of Osama bin Laden, the nightmare scenario of a terrorist exploding a nuclear bomb in a major city isn't necessarily the far-fetched stuff of movies.
"It would not take much, just a handful or so of these materials, to kill hundreds of thousands of innocent people and that's not an exaggeration, that's the reality that we face," President Barack Obama told world leaders at the meeting, a follow-up to a summit he hosted in Washington in 2010.
Building a nuclear weapon isn't easy, but a bomb similar to the one that obliterated Hiroshima is "very plausibly within the capabilities of a sophisticated terrorist group," according to Matthew Bunn, an associate professor at Harvard University's John F. Kennedy School of Government.
There's an "immense difference between the difficulty of making safe, reliable weapons for use in a missile or combat aircraft and making crude, unsafe, unreliable weapons for delivery by truck," Bunn said.
The Nuclear Threat Initiative, a Washington-based nonproliferation group that tracks the security of world nuclear stockpiles, said in a January report that 32 countries have weapons-usable nuclear materials. Some countries, such as the United States, maintain strict controls already. However others, including Russia and other former Soviet republics, have struggled to secure their stocks, raising fears of "loose nukes" falling into the hands of terrorist groups.
It's unclear how nations will enforce the summit's goal of securing nuclear material by 2014. The International Atomic Energy Agency shares best practices for securing nuclear material, but the U.N. body has no power to enforce its recommendations.
Some countries on the NTI list are a concern because of their government's ties with militant groups or because of corruption among their officials. Others simply don't yet have good safety practices.
Although Pakistan's small stockpiles of nuclear material are heavily guarded, it is believed to be prone to corruption by officials who may have sympathies to hard-line Islamic militants, Bunn said.
"At least four terror groups, including al-Qaida and Japan's Aum Shinrikyo doomsday cult, have expressed a determination to obtain a nuclear weapon," said Kenneth Luongo, co-chair of the Fissile Materials Working Group, a Washington-based coalition of nuclear security experts.