Former Georgia Senator Sam Nunn says, a new report highlights the risk that terrorists could acquire the means to build a nuclear bomb.
The report is from an institute Nunn founded with Georgia media mogul Ted Turner.
The Washington, D.C. based Nuclear Threat Initiative ranked 32 countries for how securely they manage nuclear weapons material.
The report suggests the U.S. and other nations have a long way to go toward the goal of securing materials like enriched uranium.
Nunn says, it's not a piece of cake for terrorists to make a bomb -- but not impossible, either.
"The most important thing for us to do to prevent catastrophic terrorism anywhere in the world is to secure nuclear weapons usable material everywhere it exists," Nunn says.
The Nuclear Materials Security Index ranks North Korea the least secure nation and Australia the most secure, with the U.S. at No. 13.
"As far as the United States is concerned, we do a good job in a lot of areas but we have a vast amount of the material," Nunn says. "It has to be moved and it has to be taken care of. So the more material you have, the more exposure you have."
World leaders will meet for the second of two international summits on nuclear security in South Korea in March.