Robert Farley says it isn’t:

In other words, war is not inevitable. Key people can still say no, with U.S. President Barack Obama being the most important among them. For now, the Obama administration seems to believe that pro-war rhetoric is manageable, and that it can tack between the demands of the Israeli government, the sanctions coalition and the presidential candidates of the Republican Party. This process involves pushing back against the idea that an immediate attack is necessary, while reaffirming the general idea that Iran represents a major threat to the United States.

However, it could become more difficult to avoid war in the future:

As a political strategy, this may be viable. It runs the risk, however, of creating a rhetorical trap for the Obama administration. At some point, it may be hard for Obama to step down from the idea that an Iranian nuclear weapon is unacceptable and worth a war to prevent. In that case, saying no may become too politically difficult for the president. The task for hawks, whether in the United States or Israel, will be to draw this box as tightly and narrowly as possible. It behooves the president, and opponents of conflict with Iran, to remember that nothing about war removes the threat of uncertainty. Rather, most of the problems that exist before a strike against Iran will remain afterward, just in a much less predictable environment [bold mine-DL].

This appears to be a case where military action has little or no prospect of success while also being unnecessary and therefore likely to make the situation worse than it is now. If an Iranian war can’t eliminate the perceived threat (and it can’t), there is no reason to expose Israel or the U.S. to the risks it would involve.