The issue of nuclear security is a familiar one to the United States. The country has been assisting the former Soviet Union secure its nuclear materials since the end of the cold war. During his presidential campaign Obama vowed to strengthen nonproliferation and improve global nuclear security. He proposed the nuclear security summit a year ago in Prague in his speech calling for a nuclear-free world.

The two-day summit is aimed at reaching agreement on securing all nuclear materials within four years. A joint communiqué and concrete plans are likely to be released after the meeting.

The world stockpile of nuclear materials is very large – up to 1,900 tons of highly-enriched uranium (HEU) and 525 tons of plutonium – enough to make 60,000 nuclear weapons. Stockpiles are actually increasing as more and more countries develop reactors for civil use as power stations.

Statistics from the International Atomic Energy Agency (IAEA) show that between 1993 and 2005, there were 827 cases of theft or smuggling of nuclear materials. In the year 2005 alone, 105 cases were reported.

The increase of unsecured and uncontrolled nuclear materials has resulted in a rising nuclear threat. Terrorists have been trying desperately to obtain nuclear materials. In November 2001, Bin Laden hinted that Al Qaida had acquired nuclear weapons; nuclear terrorism may not be as far away as we would like to think.

The United States is deeply concerned about the nuclear threat because it is involved in more conflicts than any other state. It sees nuclear terrorism as the biggest threat to its security.

Obama wants to use the summit to highlight the danger of nuclear terror and persuade the world to work together to lock down nuclear materials "in a very specific time frame with a specific work plan".

The summit is seeking consensus on containing nuclear terrorism and securing nuclear materials, concerns that deserve to be at the top of the international agenda.

The author is a columnist with China.org.cn. For more information please visit: http://www.h5a3.com/opinion/node_7075398.htm

(This article was translated by Fan Junmei.)