Worth noting that the Obama administration is not the only government facing tough choices about how to respond to the recent events in Iran. Germany, too, has experienced some divergences of opinion about whether a firm response on human rights should take priority over the need for a negotiated settlement to the nuclear standoff.
As for the Russians, they’re deciding whether the events should get in the way of a signed-sealed-but-not-yet-delivered contract with Tehran for S-300 missile defense systems. Richard Weitz devoted one of his WPR columns to explaining the system’s significance. In a nutshell, it would make an airstrike by Israel against Iranian nuclear installations even more difficult to pull off than it already is. That’s why Israel is currently lobbying so strongly to get Russia to forego on the deal.
If you really think an Israeli strike would be a good way to provoke a regional conflagration, the S-300s would have been an effective deterrent — were they already in place. I’m guessing that in the current climate, any move to deliver them would probably be factored into Israeli military planners’ strategic calculations, most likely as justify for accelerating any action.