Obama: Nuclear weapons biggest threat to US

US President Barack Obama's nuclear security summit will begin in Washington today (Monday). Leaders from around the world will participate in the conference and will focus on strategy to prevent nuclear weapons from falling into the hands of terrorist organizations.
Obama said the possibility of terrorists getting a nuclear device is the "single biggest threat" to U.S. security as he opened a series of meetings with world leaders on preventing the spread of atomic material.
"There's a lot of loose nuclear material around the world" and the summit's focus "is getting the international community on a path to which we are locking down" those supplies, Obama said before meeting with South African President Jacob Zuma. "We know that organizations like al-Qaida are in the process of trying to secure a nuclear weapon."
Israeli Deputy Prime Minister Dan Meridor will represent Israel at the summit.
AP contributed to this report