Israel possesses more than 300 nuclear warheads, former US President Jimmy Carter told MSNBC last week.
Carter played down Israel's ability to perform a military strike against the Iranian nuclear facilities, pointing out that only the United States can conduct such a strike.
Carter said: "It is not useful for the United States to attack Iran, even if it succeeded in producing a nuclear bomb, and I don't believe it's appropriate for the United States to bomb Iran over this issue."
Carter described demanding Iran abandon its nuclear programme as "ridiculous".
The P5+1 powers; Britain, France, China, Russia, Germany and the United States, proposed to ease sanctions imposed on Tehran if it agrees to reduce its nuclear activities to develop a nuclear weapon.