The numbers game on enrichment reveals a deeper difference: For President Obama, the trigger for military action would be a “breakout” decision by Iran’s supreme leader to go for a bomb, something he hasn’t yet done. For Netanyahu, the red line is preventing Iran from ever reaching “threshold” capability where it could contemplate a breakout. He isn’t comfortable with letting Tehran have the enrichment capability that could be used to make a bomb, even under a nominally peaceful program…

Though most members of Netanyahu’s government would probably support him, there are some subtle nuances of opinion. U.S. officials say Defense Minister Ehud Barak’s focus is stopping Iran before it enters a “zone of immunity” when it begins full operation of centrifuges buried under a mountain near Qom. Iran probably will enter this zone sometime later this year. As Israeli officials have put it, the deadline for action “is not a matter of weeks, but it’s not a matter of years, either.”…

Some Israeli experts are skeptical about the “zone of immunity” timeline. They believe that no facility, even the hardened site at Qom, is invulnerable to a clever attack: Iran will have immunity only with an actual nuclear-weapons umbrella.