If the Obama administration feels that there is even a faint chance to reach a lasting agreement with Iran, President Obama can improve the odds by insisting on a few conditions and satisfy itself and its allies that it has done all it could to prevent the military option.
In an Israeli-Iranian confrontation, who would their leaders call? How would they communicate? There may be backchannels but these are slow, cumbersome and unreliable. The danger of a catastrophe would be unacceptably high.
Ultimately, the U.S. will one day leave Afghanistan -- and it may be sooner than anyone expects. The key here is to leave in a way that promotes regional stability and cooperation, not a power vacuum that could foster proxy conflicts.