<P> Opened for signature in 1968 , the treaty entered into force in 1970 . As required by the text , after twenty - five years , NPT Parties met in May 1995 and agreed to extend the treaty indefinitely . More countries have adhered to the NPT than any other arms limitation and disarmament agreement , a testament to the treaty 's significance . As of August 2016 , 191 states have adhered to the treaty , though North Korea , which acceded in 1985 but never came into compliance , announced its withdrawal from the NPT in 2003 , following detonation of nuclear devices in violation of core obligations . Four UN member states have never accepted the NPT , three of which are thought to possess nuclear weapons : India , Israel , and Pakistan . In addition , South Sudan , founded in 2011 , has not joined . </P>
<P> Opened for signature in 1968 , the treaty entered into force in 1970 . As required by the text , after twenty - five years , NPT Parties met in May 1995 and agreed to extend the treaty indefinitely . More countries have adhered to the NPT than any other arms limitation and disarmament agreement , a testament to the treaty 's significance . As of August 2016 , 191 states have adhered to the treaty , though North Korea , which acceded in 1985 but never came into compliance , announced its withdrawal from the NPT in 2003 , following detonation of nuclear devices in violation of core obligations . Four UN member states have never accepted the NPT , three of which are thought to possess nuclear weapons : India , Israel , and Pakistan . In addition , South Sudan , founded in 2011 , has not joined . </P>
when did the nuclear non proliferation treaty start
when did the nuclear non proliferation treaty start
1970
1970