From the Israeli perspective, the fear is that if pressure is off of Iran, Israel would be left having to accept the balance of power in the region significantly shifting toward Iran. It's not an existential threat, but it would definitely be a problem for Israel.
Trita ParsiUnfortunately, every time the United States has tried to pursue a peace deal between the Israelis and the Palestinians by beating back Iran and trying to isolate Iran, it has failed. And it has failed under much better circumstances.
Trita ParsiNIE presents a major obstacle to those who are pushing for military confrontation. In many ways it is a severe blow to their agenda. However, I wouldn't go as far as to say that the risk has been significantly reduced or eliminated.
Trita ParsiIran has, by virtue of its growth and by virtue of the United States' mistakes in Iraq, tilted the balance of power in the Middle East. That is the case, but that doesn't necessarily mean it is a threat.
Trita ParsiBeyond that is the fear that the United States will end up negotiating and agreeing to a deal with Iran. The Israelis do not like that either because they fear the deal will come at the expense of Israel's security interests. From an Israeli perspective, the NIE makes the risk of some sort of settlement much greater.
Trita ParsiThe United States has weakened itself with Iraq; Iranians feel victorious - they feel capable of filling the void. I think from the very outset the nuclear issue has been secondary to the more strategic outlook, in which the United States has, since 1991, pursued a policy that it cannot permit any country in the region to become too powerful and challenge American hegemony.
Trita Parsi