When Iran’s new President Hassan Rouhani came home from the United Nations General Assembly meeting last Friday, demonstrators at Tehran airport threw eggs, shoes and stones. They had heard about his 15-minute phone conversation with U.S. President Barack Obama, and they were not pleased.

But there were many more Rouhani supporters at the airport, who clearly hoped that he will make a deal with the United States on Iran’s nuclear program and end the sanctions that are strangling the Iranian economy.

“I believe we can reach a comprehensive solution,” Rouhani’s office tweeted after the famous phone call to Obama, and most Iranians want to believe him.

Most people elsewhere want to believe him too. We have had 10 years of escalating threats by Israel and the U.S. to attack Iran if it doesn’t stop enriching uranium for its civil nuclear power program, on the grounds that this is merely a cover for a nuclear weapons program. And everybody understands that this could end up as a big, ugly war.

That’s why Obama took the political risk of becoming the first U.S. president in 34 years to talk to an Iranian leader. When he addressed the General Assembly in New York, he welcomed the “more moderate course” taken by Rouhani, who took office in August. “The roadblocks may prove to be too great,” Obama said, “but I firmly believe the diplomatic path must be tested.”

Then the chief roadblock arrived: Israeli Prime Minister Benjamin Netanyahu. He was flying to New York to “tell the truth in the face of the sweet talk and the blitz of smiles,” he said — and when he mounted the podium at the General Assembly, he bluntly accused the new Iranian president of being “a wolf in sheep’s clothing.”

Nobody, not even the Israeli intelligence services, accuses Iran of working on nuclear weapons right now. The U.S. Central Intelligence Agency flatly says that it is not. The accusation, by Israel, its Western supporters, and some of Iran’s Arab neighbors, is that Tehran is building a (quite legal) uranium enrichment capability in order to be able to make actual nuclear weapons at some future time.

Iran denies any such intention, of course. “We say explicitly that we will be transparent; we say explicitly that we will not build a bomb,” said Rouhani in New York. “No nation should possess nuclear weapons, since there are no right hands for these wrong weapons.”

That last was a subtle slap at the hypocrisy of the U.S. and Israel, which have thousands and hundreds of nuclear weapons respectively, for threatening to attack another country because it is allegedly planning to build them in the future. But Rouhani is not demanding that Israel give up its nuclear weapons and sign the Nuclear Non-Proliferation Treaty. On the contrary, he implicitly accepts the status quo.

So why doesn’t Netanyahu welcome the possibility that Iran now seems willing to negotiate a deal that would leave it free to make its own enriched nuclear fuel for reactors, but stop it from making highly enriched uranium suitable for weapons? By all means insist that any U.S.-Iranian deal be enforceable and free of loopholes, but why say things like “Rouhani thinks he can have his yellowcake (enriched uranium) and eat it too”?

The 10-year confrontation over Iran’s alleged nuclear weapons ambitions has served Netanyahu well. It has distracted the world’s attention from the plight of the Palestinians in the occupied territories. It has also given him enormous leverage in Washington: much U.S. policy in the Middle East is driven by the perceived need to keep Israel from launching a unilateral attack on Iran, which would be a catastrophe for American interests in the region.

But if Netanyahu truly believes that Iranian nuclear weapons would be an existential threat to Israel, why would he oppose negotiations that might put an end to that possibility? Exactly what would be lost by giving peace a chance?

What would be lost, if a lasting deal emerged from the negotiations being mooted between Tehran and Washington, is the ability of successive right-wing Israeli governments to extort unconditional American military support for Israel, no matter what it does, precisely because it allegedly faces an existential threat from Iran.

Since the Russian-sponsored deal over Syria’s chemical weapons has similarly sidelined the prospect of an American attack on Syria (which Israel sees as its second most dangerous enemy), the foreign policy that has sustained Netanyahu for almost two decades is collapsing.

Without a plausible military threat to Israel — and where else could it come from, if not Iran or Syria? — his ability to bully successive American administrations into ignoring Israel’s illegal settlements on occupied Palestinian land, its clandestine nuclear and chemical weapons, and much else besides, would slowly drain away. So Netanyahu will do everything he can to strangle the newborn possibility of an American-Iranian rapprochement in its cradle.

As the scenes at Tehran airport demonstrate, Rouhani also faces strong opposition at home from those whose political instincts or interests demand a continuation of the Iran-against-the-world confrontation that has already lasted for a generation. Rouhani’s initiative has created a great deal of hope, but its enemies are already working to kill it.

Gwynne Dyer is an independent journalist whose articles are published in 45 countries.