Just To Reiterate

Iran is one of the signatories of the Nuclear Non-Proliferation Treaty.

Safari: Iran not to withdraw from NPT
"Iran's deputy foreign minister for European affairs says Tehran will never withdraw from the Nuclear Non-Proliferation Treaty (NPT). "The Islamic Republic of Iran has taken all the necessary confidence-building measures from the beginning of its nuclear program," Mehdi Safari said in a press conference which was held in Iran's embassy in Berlin on Friday. "As President Ahmadinejad and the Secretary of Iran's Supreme National Security Council (SNSC) Saeed Jalili have declared Iran will continue its cooperation with the IAEA in the framework of its regulations," he added."

Israel isn't a cosignatory of the Nuclear Non-Proliferation Treaty.

(UN transcript)
"Israel is continuing with its policy of expansion, occupying Palestinian territory as well as the territory of two Arab States. For this expansionist policy, it depends on a huge arsenal of weapons of mass destruction — nuclear, chemical and biological — as well as conventional missiles. It is the only State in the area that has not yet acceded to the NPT."