Fact Sheet: Nuclear Non-Proliferation Treaty (NPT)

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The Treaty on the Non-Proliferation of Nuclear Weapons (also known as the Nuclear Non-Proliferation Treaty, or NPT) is an international agreement designed to prevent the spread of nuclear weapons, promote cooperation between states on peaceful uses of nuclear energy, and advance nuclear disarmament.

The NPT was opened for signature on July 1, 1968, and the treaty went into force in 1970. 191 countries are now a party to the NPT. South Sudan, India, Pakistan, and Israel have never joined the NPT. North Korea joined the NPT in 1985, but withdrew in 2003.

The treaty’s term was originally 25 years, but it was extended indefinitely at a review conference in 1995.

Why It Matters

During a speech in 1963, President John F. Kennedy warned of a world with 25 nuclear weapons states or more. Today, only nine are believed to possess nuclear weapons. The NPT has helped prevent the spread of nuclear weapons, while providing the basis for non-proliferation cooperation between nuclear and non-nuclear states. In the interest of broadening access to nuclear energy for peaceful purposes, states that are party to the NPT agree to the “fullest possible exchange” of materials, equipment, and expertise.

What It Does

Nuclear Weapons States and Non-Nuclear Weapons States

The NPT distinguishes between nuclear-weapons states (NWS) and non-nuclear-weapons states (NNWS). Nuclear Weapons States are the five states that possessed nuclear weapons when the treaty was signed in 1968: the United States, the Soviet Union, the United Kingdom, France, and China. The Russian Federation replaced the Soviet Union as a NWS after the disintegration of the Soviet Union. Independent former Soviet states have joined the NPT as NNWS. With the exception of the five states recognized as NWS in the treaty, states may only join the NPT as NNWS.

Non-Proliferation The NPT prohibits NNWS from developing or acquiring nuclear weapons, and prohibits NWS from transferring nuclear weapons or control of such weapons to non-nuclear states. NWS are also prohibited from assisting, encouraging, or inducing NNWS to attain nuclear weapons.

Peaceful Use

The NPT allows for the exchange of nuclear material, technology, and expertise to NNWS for use in civilian nuclear programs, as long as they do not develop nuclear weapons. The International Atomic Energy Agency (IAEA) monitors non-nuclear weapons states’ civil nuclear programs to ensure that they are not developing nuclear weapons.


Parties to the treaty are required to pursue the reduction of nuclear arsenals in good faith and, though a timeline is not included, the eventual elimination of nuclear weapons. Because the United States and Russia possess over 93% of the world’s nuclear weapons, they share much of the responsibility for disarmament.

Verification and Monitoring

The IAEA monitors the compliance of non-nuclear-weapons states. It assesses civilian nuclear programs and verifies that NNWS are not developing nuclear weapons. In order to perform this function, the IAEA establishes Comprehensive Safeguards Agreements with NNWS. NNWS may also implement the Additional Protocol, which gives the IAEA supplementary legal authority to verify a state’s safeguards obligation by expanding the organization’s rights to access information and sites to fill in gaps of information reported via safeguards agreements. All five NWS also have signed Additional Protocol agreements with the IAEA.

Every 5 years, Parties to the NPT gather for a review conference to evaluate proliferation concerns and what progress has been made towards eventual global disarmament.   

Sources: U.S. Department of State, International Atomic Energy Agency, United Nations Office for Disarmament Affairs, U.S. Congressional Research Office, Bulletin of the Atomic Scientists’ Nuclear Notebook