The two-day nuclear security summit is scheduled to open on Monday in Washington, gathering the international community to discuss securing vulnerable nuclear materials and preventing acts of nuclear terrorism.

One of the world's efforts for nuclear non-proliferation and disarmament is the publication of the Treaty on the Non-Proliferation of Nuclear Weapons (NPT). The following is a brief introduction to the NPT.

In the 1960s, the United States and the Soviet Union stepped up their nuclear testing in a bid to improve their nuclear arsenals. Seeking to maintain their respective nuclear advantages, the two superpowers began to push for negotiations on a treaty that would stem the proliferation of nuclear weapons.

In June 1968, the UN passed the NPT, which was opened for signatures in Washington, Moscow and London the next month. 59 countries signed up to it.

With 11 articles, the treaty stipulates that each nuclear-weapon state (NWS) refrain from transferring nuclear weapons or other nuclear explosive devices to any recipient, and not to assist any non-nuclear weapon state in producing or acquiring such weapons or devices.

The treaty also says that a Non-NWS should not produce or acquire nuclear weapons.

On March 5, 1970, the treaty entered into force, with a valid period of 25 years. Until now, a total of 189 countries have signed it.

In April 1995, NPT signatories held their regular 5-year-review meeting at the UN headquarters and decided to make the treaty permanent.

China acceded to the NPT in March 1992, and adheres to comprehensive prohibition and thorough destruction of nuclear weapons. China also has been firmly opposing nuclear weapons proliferation and actively promoting peaceful use of nuclear energy.