WASHINGTON — Israeli Prime Minister Benjamin Netanyahu’s speech to the United States Congress was eloquent, moving and intelligent in identifying the problems with the potential nuclear deal with Iran. But when describing the alternative to it, he entered Never-Neverland, painting a scenario utterly divorced from reality. Congress joined him on his fantasy ride, rapturously applauding as he spun out one unattainable demand after another.

Netanyahu declared that Washington should reject the current deal, demand that Tehran dismantle almost its entire nuclear program and commit never to restart it. In the world according to Bibi, the Chinese, Russians and Europeans will cheer, tighten sanctions, and increase pressure — which would then lead Iran to capitulate. “Dreams do come true, if only we wish hard enough,” said Peter Pan.

We actually have some history that can inform us on the more likely course. Between 2003 and 2005, under another practical president, Mohammad Khatami, Iran negotiated with three European Union powers a possible deal to place Iran’s nuclear program under constraints and inspections. The chief nuclear negotiator at the time was Hassan Rouhani, now Iran’s president.

Iran proposed to cap its centrifuges at very low levels, keep enrichment levels well below those that could be used for weapons, and convert its existing enriched uranium into fuel rods (which could not be put to military use). Peter Jenkins, the British representative to the International Atomic Energy Agency, told the Inter Press Service later, “All of us were impressed by the proposal.” But the talks collapsed because the Bush administration, acting through the British government, vetoed it. It was certain, Jenkins explained, that if the West could “scare” the Iranians, “they would give in.”

What was the result? Did Iran return to the table and capitulate? No, the country withstood the sanctions and, unimpeded by any inspections, massively expanded its nuclear infrastructure. Iran went from 164 centrifuges to 19,000, accumulated over 17,000 pounds of enriched uranium gas, and ramped up construction of a heavy water reactor at Arak that could be used to produce weapons-grade plutonium.

Harvard University’s Graham Allison, one of the country’s foremost experts on nuclear issues, pointed out that “by insisting on maximalist demands and rejecting potential agreements, the first of which would have limited Iran to 164 centrifuges, we have seen Iran advance from 10 years away from producing a bomb to only months.”

If the deal now being negotiated fails, the most likely scenario is a repetition of the past. Iran will expand its nuclear program. If the other major powers believed that Iran’s offer was serious but U.S. and Israeli intransigence torpedoed it, they will be reluctant to enforce sanctions — and all sanctions start to leak over time anyway. Netanyahu worries that with this deal, 10 years from now Iran might restart some elements of its programs. But without the deal, in 10 years Iran would likely have 50,000 centrifuges, a massive stockpile of highly enriched uranium, new facilities, thousands of experienced nuclear scientists and technicians, and a fully functioning heavy water reactor that can produce plutonium. At that point, what will Bibi do?

The theory that Iran will buckle under continued pressure ignores certain basic facts. Iran is a proud, nationalistic country. It has survived 36 years of Western sanctions, through low oil prices and high oil prices. It endured an eight-year war with Iraq in which it lost an estimated half a million men. The nuclear program is popular, even with leaders of the pro-democratic Green Movement.

As Allison points out, Iran already has the capacity to build a nuclear weapons program and got it in 2008 when it mastered the ability to produce centrifuges and enrich uranium. And yet, Iran has not actually done it. For almost 25 years now, Netanyahu has argued that Iran is on the verge of producing a nuclear weapon. In 1996 — 19 years ago — he addressed the U.S. Congress and made pretty much the same argument he made this week. Over the past 10 years he has argued repeatedly that Iran is one year away from a bomb.

So why have Bibi’s predictions been proved wrong for 25 years? A small part of it has been Western and Israeli sabotage that impeded Iran’s progress. But even the most exaggerated claims by intelligence agencies would not account for a delay of more than a few years. The larger part is probably that Iran has always recognized that were it to build a bomb, it would face huge international consequences. In other words, the mullahs have calculated — correctly — that the benefits of breakout are not worth the costs. The key to any agreement with Iran is to keep the costs of breakout high and the benefits low. This is the most realistic path to keeping Iran from becoming a nuclear weapons state — not Peter Pan dreams.

Fareed Zakaria’s email address is comments@fareedzakaria.com.