Thousands of nuclear weapons still pose global threat

• There are 25,000 to 30,000 assembled nuclear weapons in the world, more than 90 percent of them in the United States or the countries that made up the Soviet Union, said Matthew Bunn, a researcher at Harvard's Kennedy School of Government.

• The nuclear threat today is as great as it was during the height of the Cold War, but now the threat comes from many different areas and not one place, according to Daryl Kimball, executive director of the Arms Control Association.

• Many feared in the 1960s that dozens of countries would develop nuclear weapons, but the number has been limited to a handful because of nonproliferation agreements, said political scientist Dan Reiter of Emory University.

• One of the biggest threats from new countries like Iran getting nuclear weapons is that it could erode the network of treaties and agreements preventing nuclear proliferation because neighboring countries would push to get their own, said Joseph Cirincione of the Carnegie Endowment for International Peace.

• Over 180 governments will gather at the United Nations in May to review progress on meeting their obligations under the 1968 Nuclear Non-Proliferation Treaty, intended to control the spread of nuclear weapons.