From all appearances, Iran is a rational state, acting responsibly. Therefore, the US believes it should not go to war to stop Iran. Since it is desirable to not increase the number of states having nukes, the US will continue to help by "threats." But Israel hould know that there will no US action. And if Israel acts alone against Iran, the US will not intervene on her behalf. It will be a private Israeli affair. If Israel choses to reveal this to the world, too bad, because then Iran will probably nuclearize quickly.
Three minors arrested in Jaffa for throwing rocks at a bus; no injuries reported (Haaretz)
from the article: Israel, U.S. discuss triggers for military strike on Iran