The Universal Nuclear Non-Proliferation treaty was signed by 189 states. Israel is not among them. Neither were India and Pakistan, now nuclear-armed. On the other hand, as an Israeli official pointed out, Iran, Iraq, and Libya are signatories, and they have or sought nuclear reactors. Therefore, said the official, joining that pact does not end nuclear proliferation.
U.S. Assistant Secretary of State Rose Gottemoeller nevertheless asked Israel to join the treaty. If it did, it would be asked to give up any nuclear weapons it has (http://www.israelnationalnews.com/ -- Arutz-7, 5/6).
Pres. Obama is striving for nuclear disarmament. Rogue states, however, sign treaties without complying with them. They have proved they can develop nuclear capability regardless of treaties. At least, the current treaty has such big loopholes, they seem to have been designed by Congressional lobbyists.
Considering that the world is in a state of jihad, that even before the rise of Radical Islam, Arab states would gang up on Israel, that Arab states have developed other weapons of mass-destruction, and that US policy would make Israel more vulnerable without bringing Muslim states to tolerance and peace except for a phony treaty, Israel both needs nuclear arms for enemies that it can deter and to destroy the nuclear factories of Iran, which cannot be deterred.
(If you click on my category of "U.S.," you will be able to access numerous articles showing a pattern of anti-Zionist bias in the Obama regime. It started as speculation about the anti-Israel slant of his advisers, but now in office, he has pressed Israel to join his appeasement of the worst menace to civilization since the Nazi and Soviet imperialism, the threat from Radical Islam.)