For the moment, all is sweetness and light between President Barack Obama and Israeli Prime Minister Benjamin Netanyahu.

But just wait. This will almost surely change.

Netanyahu delivered a tough speech on Iran this week to a United Nations General Assembly that didn't want to hear him, and a slightly more nuanced message to Obama, who apparently did. The two men, in their last encounter, seemed to get along surprisingly well, given that they don't actually like or trust each other.

Netanyahu's message to the UN was simple: I will sooner bomb Iran than have the Jewish people threatened with nuclear annihilation.

The message to Obama was slightly more complicated: I trust you on Iran, partly because I have no choice. I'm glad you've been a stalwart on enforcing sanctions, and I appreciate your cynicism about Iran's intentions, but I can't wait forever. If Iran doesn't abandon its nuclear ambitions in the coming months, we're going to have a crisis.

"Israel will not allow Iran to obtain nuclear weapons, even if we have to stand alone," Netanyahu told the UN. He made essentially the same promise to the president, couched more diplomatically.

For now, Netanyahu and Obama are mostly in sync on this issue. Obama's sanctions regime, which has done great damage to Iran's economy and forced its leaders to at least pretend they're interested in negotiations, obviously has Netanyahu's endorsement. The White House seems hesitant to intensify the sanctions now that talks seem more likely, but it also doesn't want to prematurely ease them without gaining real concessions.

And Netanyahu's threats against Iran's nuclear program have obviously helped Obama make the argument for tough sanctions. The president has also shown no signs of wavering from his commitment to prevent Iran from gaining a nuclear weapon, and the idea of "containment" -- accepting the inevitability of a nuclear Iran and boxing it in accordingly -- doesn't seem to be in the cards.

But a conflict between the two men is almost surely coming, perhaps by next spring. Netanyahu's demands include that Iran permanently freeze its uranium enrichment, close nuclear facilities and remove the uranium it has already enriched. These are demands that Iran surely won't agree to, and I doubt Obama will adopt Netanyahu's maximalist position.

So here are three scenarios that might play out in the next few months.

The first is that Iran miraculously agrees to wind down its nuclear program to a point close to Netanyahu's demands. I don't think this will happen for any number of reasons, including because it isn't in the regime's best interest. (I wrote about why I don't think Iran is serious about negotiating an end to its nuclear program here.)

The second scenario is that Iran treats the negotiations so unseriously, and is so unwilling to concede anything to the international community, that Obama is forced to walk away from talks and redouble sanctions. This also seems unlikely, because the regime knows better now than to wander into such a trap. One of the reasons that the amiable, even charming, Hassan Rouhani is now the president of Iran -- and not an unhinged, Holocaust-denying sort like his predecessor Mahmoud Ahmadinejad -- is that Iran's supreme leader and other senior figures realized that the Ahmadinejad approach to the nuclear issue wasn't helping their cause.

The third and more likely scenario is that negotiations begin in earnest and the Iranians make an early show of cooperation. But then they only agree to give up aspects of their nuclear program that aren't central to their core goal, which is to have a program in place that would allow them to build a deliverable nuclear weapon in a matter of weeks, should the supreme leader decide he needs it. Talks could drag on for months, and the Iranians could work toward this goal while engaging in a facsimile of negotiation.

This is Netanyahu's great fear (and the fear of Iran's many Arab foes). The question on Netanyahu's mind is simple: Will the Iranians be clever enough to drag out talks and eventually propose a solution that Obama finds acceptable -- but that the Israelis do not?

The likelihood of this seems moderately high. Obama would clearly like to resolve this issue without going to war. If he thinks a negotiated settlement would keep a nuclear bomb out of Iranian hands, even if the agreement left Iran with the capability to restart its program, he might just approve it. For Netanyahu, this would be unacceptable.

And so Netanyahu and Obama, who claim today to share the same goal, might find, come spring, that they don't. And then Netanyahu will have to make a choice: Does he try to prevent Iran from gaining hold of the bomb by any means necessary and risk the wrath of the American president? Or does he keep quiet as Iran moves ever closer to becoming a nuclear state?

(Jeffrey Goldberg is a Bloomberg View columnist. Follow him on Twitter.)