President Donald Trump explained his demand for a ceasefire between Israel and Iran with one of the most pungent presidential comments ever made about the Middle East: “We basically have two countries that have been fighting so long and so hard that they don’t know what the f— they’re doing,” he told reporters on Tuesday morning.

Assuming that Trump can make the two sides stop shooting, what’s next is a period of negotiations. In this phase, Israel knows what it wants — a verifiable, ironclad agreement to prevent Iran from ever producing a nuclear weapon. If Iran won’t agree to dismantle what’s left of its nuclear infrastructure and remove its existing stockpile of highly enriched uranium, this war could start again.

The key intermediary in the negotiation that’s ahead might be Qatar. Envoys from that tiny emirate — which houses a U.S. base that was struck by Iranian missiles in a retaliatory raid on Monday — have talked regularly with all three sides during the crisis. They helped Trump achieve his breakthrough ceasefire. But their work is just beginning.

Negotiators will confront this essential problem: Iran has been lying about its activities for more than 20 years. It said it wasn’t trying to make a bomb even as it allegedly gathered — and regathered — its top scientists to push toward weaponization. It claimed to be leveling with the International Atomic Energy Agency, but the IAEA concluded last month that it wasn’t.

Israeli intelligence, backed by IAEA investigations, shows that after Iran ceased a weaponization program known as Amad in 2003, it secretly reconstituted a new effort to pursue similar research.

Iran crossed what Israelis considered a red line in this resumption of its weaponization effort over the past several years. Indeed, this renewed push to make a bomb — as opposed to just enriching the fuel for one — was probably the trigger for the devastating war that Israel began on June 13 and ended, at least temporarily, with Monday night’s ceasefire.

Israeli intelligence on Iranian weaponization was shared with me by a source familiar with the reports. Much of it tracks IAEA reports published on June 12 with the agency’s stern warning that it couldn’t “provide assurance that Iran’s nuclear programme is exclusively peaceful.” Trump has received much more detailed information from Israel, and officials say that’s why he stated last week that Iran was actively seeking to build a weapon, despite a statement to the contrary in March by his own director of national intelligence, Tulsi Gabbard.

Who is right about weaponization — Israeli or American intelligence analysts? To make a firm judgment, you would need much more evidence than I reviewed. But based on what I saw, I would be surprised if the House and Senate intelligence committees didn’t conclude that U.S. analysts were being too cautious in preparing Gabbard’s March 26 testimony, during which she said the intelligence community “continues to assess that Iran is not building a nuclear weapon.”

Intelligence reporting on Iran’s weaponization program has a cat-and-mouse element, but sources familiar with Israeli intelligence shared with me a timeline showing what they believe happened — based in part on a cache of secret bombmaking plans their spies discovered in a Tehran warehouse in 2018.

The Amad bombmaking effort started around 2000, Israeli analysts believe. At secret sites in Varamin and Lavisan-Shian around Tehran, the Iranians explored highly technical problems. These included systems like a “neutron trigger” at the bomb’s center that would initiate a chain reaction, specialized plastic explosives for a “shockwave generator” to ensure simultaneous detonation around the shell of the weapon and other complex features.

The CIA revealed this weaponization effort in 2007 but concluded that it had stopped in 2003. But the IAEA later found evidence that equipment from the secret Amad sites had been shifted after 2003 to a warehouse in Turquzabad, near Tehran. When Israel discovered the cache of Amad documents in 2018, the nuclear gear was moved once again, Israeli and IAEA documents indicate.

An IAEA report this month said the secret facilities at Lavisan-Shian, Varamin and other locations “were part of an undeclared structured nuclear program carried out by Iran until the early 2000s,” and that contaminated equipment from these sites was moved to Turquzabad “until 2018, after which items were removed.”

Iran’s renewed weaponization program was called SPND, known in English as the Organization of Defensive Innovation and Research, according to the Israeli document. Israel claims the organization had been established in 2011 by Mohsen Fakhrizadeh Mahabadi, an Iranian nuclear scientist who was assassinated by Israel in 2020.

SPND’s key sites were at Shariati, in Tehran, and Sanjarian, near Parchin in southeastern Iran. The Shariati complex “is part of Iran’s concealment and deception efforts” and houses some of its technical laboratories and workshops, along with equipment transferred from Turquzabad, according to the Israeli dossier. The site was struck by Israeli jets on June 13, along with its chief Mansour Asgari, an Iranian physicist.

The Sanjarian site, which had produced detonators for Amad and similar equipment for SPND, is now nominally operated by a commercial company. It was also struck last week by Israeli jets.

Iran’s alleged weaponization infrastructure is now in ruins. Israel has destroyed the equipment — and killed the researchers — that were part of what appears to have been a secret bombmaking effort dating back 25 years.

The most urgent postwar challenge will be finding — and destroying — Iran’s stockpile of 400 kilograms of 60% enriched uranium, which could become fuel for a “dirty bomb” in weeks if it isn’t controlled. Iran’s Isfahan nuclear facility, where this material was thought to be held, was bombed by both Israel and the United States. But the New York Times reported that IAEA director Rafael Grossi believed it had been moved before the attack.

Israeli and American sources say they know where the 400 kilograms are located. We can only hope so. They need to find it — quick — and dispose of it safely. Otherwise, the fuse on the Iranian bomb is still lit.

David Ignatius writes a twice-a-week foreign affairs column for The Washington Post. His latest novel is “Phantom Orbit.” He is on X: @ignatiuspost.