The nuclear Non-Proliferation Treaty came into force in 1970, following widespread international concern about the risk of nuclear weapons proliferation and the spiraling nuclear weapon stocks of those states that had developed them.
The NPT is a multilateral treaty aimed at limiting the spread of nuclear weapons including three elements: (1) non-proliferation, (2) disarmament, and (3) peaceful use of nuclear energy
States without nuclear weapons will not acquire them;
States with nuclear weapons will pursue disarmament;
All states can access nuclear technology for peaceful purposes, under safeguards.
According to the treaty the nuclear weapon states are the United States, UK, Russia, China and France.
Three states, Israel, India and Pakistan did not sign the NPT.
They stayed outside the treaty framework and have developed nuclear weapons.
North Korea signed the treaty but withdrew from it in 2003.