They are going to develop it anyway, it's 1940's technology. If Iran developed a peaceful nuclear program, with Israeli help, it would be very difficult for the Ayatollah to then convince the Iranian people that they must enhance the program to weapons grade because of the threat from Israel. And even if they did, wouldn't it be better to have developed relations prior to that day?
Roadside bomb kills five border officers in western Iraq (AP)
from the article: Iran's Khamenei: We will destroy Israeli cities if attacked