Israel's Netanyahu Tries to Get Between Obama and Iran Abir Sultan / Reuters Israel's Prime Minister Netanyahu attends the weekly Cabinet meeting in Jerusalem Winging his way to Washington on Sunday for a meeting with President Barack Obama on Monday, Israeli Prime Minister Benjamin Netanyahu tried to deflate the new spirit of diplomacy that's blossomed between the U.S. and Iran. A post appeared on his Twitter account, perhaps from 11,000 m in the air, perhaps from the desk of a PR functionary back in Jerusalem. It didn't really matter. In the big picture, he was the dad standing at the top of the stairs, glowering at a pair of teenagers who had gotten a little too friendly too quickly on the davenport below. "I will tell #truth in face of the sweet-talk and the onslaught of smiles," the post read. One must talk facts and one must tell the truth. The incipient rapprochement between Washington and Tehran has in its first flush the feel of a sudden new relationship that's caught both sides a bit by surprise, taking off with a speed that carries a danger of overheating. After the wild weekend, enter the chaperone. Netanyahu stood stolidly by when Obama placed his call to Iranian President Hassan Rouhani on Friday, and held his peace while the words that passed between them were recounted with a breathless excitement associated with middle-school romance. Afterward, Rouhani (who has his own dad to answer to back in Tehran) was like a teenager gobbling breath mints - actually deleting posts put up in the flush of the moment. "Things are going really, really fast - faster than expected," the New York Times" ace in Tehran, Thomas Erdbrink, quoted a conservative Iranian journalist as saying. Netanyahu's job - at the White House, where he will meet Obama on Monday, and at the U.N., where he will speak on Tuesday, and in a great many media interviews all week long - is to slow things down. The method he appears to have in mind is weight, lots and lots of weight - the accumulated factual record about Iran's nuclear program, the issue that brought Obama and Rouhani together. Until a couple of weeks ago, it was not a plot point in a rom-com but what historians call a casus belli, a justification for war. MORE: Iran's President Hassan Rouhani at the U.N. General Assembly: Three Takeaways The Israeli reality check will take the form of details - the number of centrifuges spinning in the underground Natanz plant and heavily fortified Fordow, the progress on the heavy water reactor being built at Arak, which will be able to produce plutonium. There's no need to get into any new intelligence. To dissipate the frothy air of possibility that Rouhani left in his wake, the files posted online at the U.N."s International Atomic Energy Agency (IAEA) say all most people need to know about an oil-rich country that, more than a decade ago and in secret, set out to master every element of the nuclear-fuel cycle. In the hours before he left for Washington, Netanyahu was immersing himself in the data at length, Shimon Shiffer writes in the Israeli daily Yedioth Ahronoth: "He intends to share this information with Obama." And, on Tuesday, he'll do the same with the global audience from the familiar green rostrum of the General Assembly, where Netanyahu will be the last speaker of the annual convocation. A year ago, Netanyahu stole the show by holding up a cartoon bomb - a gimmick, but one that succeeded in keeping control of the narrative of the Iranian nuclear threat. Netanyahu (and then Defense Minister Ehud Barak) had done a remarkable job of bringing Iran's ambiguous program to the top of the global agenda, most effectively by timing their own unsubtle threats of air strikes as a drumroll for the release of a damning IAEA report. The Iran of then President Mahmoud Ahmadinejad did its part too, galvanizing the world's diplomatic community against it by allowing thugs to overrun the British embassy just a couple of weeks later. MORE: Obama to U.N.: Diplomacy With Iran "Must Be Tested" But the rise of Rouhani, with the assent of Supreme Leader Ali Khamenei, has taken control of the narrative away from the Jewish state. That matters, as the issue enters the realm of high-level diplomacy, because it's not yet clear whether Israel and the U.S. share the same definition of an acceptable outcome. It's a major reason for Israeli unease with the enthusiasm over the phone call and the momentum it brings. All of which will feed a fresh round of speculation about Netanyahu's relationship with Obama - a troubled one for the four years of the American's first term, then recast as a "buddy movie" during Obama's state visit earlier this year. The American President left Israel bewitched. But that was before he called the newly minted President of Israel's worst enemy on the way to the airport. Afterward, the White House broadcast assurances that Israel was told the call would happen before it went through. But in Israel the Sunday papers hinted not all was well. "Obama presented Netanyahu with a done deal," wrote Yedioth columnist Nahum Barnea, widely respected and no apologist for Netanyahu. The advance warning about the phone conversation with Rouhani, which was given to National Security Adviser Major General Yaakov Amidror prior to the conversation, was a joke. Obama neither consulted with Netanyahu nor did he take his position into account. So the table is set for more drama, if dramatic is how Bibi chooses to play it. Two-and-a-half years ago, he sat in the Oval Office and lectured Obama on the history of the Palestinian conflict as cameras rolled. The Premier has lost a noticeable amount of weight recently, but can still play the heavy. Given the extraordinary amount of cooperation between governments as a matter of routine, though - and substantial investment both leaders have made in improving their personal dynamic - look for a more restrained dynamic in the White House. From a concerned dad who everyone knows has #truth on his side, a raised eyebrow can work wonders. MORE: Iran President Rouhani's Real Challenges