Oversights Mar Low-End Estimate of Tehran’s Nuclear Weapons Timeline

U.S. intelligence assessments have concluded that Iran is now 9 to 12 months away from being able to build a nuclear weapon, according to a Reuters report.

Taken at face value, the report would indicate that the U.S.-Israeli air campaign this year did not drastically increase the time Iran requires to build a bomb; prior to this conflict and the 12-Day War, U.S. intelligence reportedly placed Iran’s breakout time at three to six months.

The assessments, however, deserve context. A well-placed Middle Eastern source familiar with both U.S. and Israeli estimates told FDD that the latest figure represents a worst-case scenario unsupported by post-strike realities or Iran’s actual capabilities. The source said it does not reflect the majority view in the U.S. intelligence community or Israel’s assessments. In July 2025, the Pentagon estimated that the June strikes had pushed Iran back to roughly two years from building nuclear weapons, while CIA Director John Ratcliffe stated they set Iran back by “years.” Israeli estimates place the timeline at two to three years. Strikes this year likely extended the timeline even further.

The selective leak of this worst-case estimate appears politically motivated and timed to undermine support for the U.S. and Israeli military campaigns against Iran.  

Estimate of 9-12 Months Based on Improbable Assumptions

Both the pre- and post-June 2025 estimates likely refer to Iran’s timeline for assembling a crude nuclear device — a bomb built quickly, without rigorous testing or a sophisticated detonation system. This may assume the use of 60 percent highly enriched uranium (HEU) as fuel, or alternatively, time to produce 90 percent weapons-grade uranium (WGU) — the preferred purity for nuclear weapons — from the HEU and weaponize it. Before the June 2025 strikes, Iran could produce enough WGU for 11 nuclear weapons in one month, and enough WGU for another 11 weapons over the next four months.   

The estimate likely assumes Iran can retrieve roughly five bombs’ worth of HEU — and possibly 20 percent enriched uranium stocks — still entombed in tunnels near Esfahan, and reconstitute uranium metal production, weaponization capabilities, and expertise. Yet conditions on the ground belie these assumptions.

Strikes Have Created Barriers to Key Nuclear Activities

Although Iran may still technically access some HEU stocks, President Donald Trump has repeatedly stated that the United States and Israel maintain round-the-clock surveillance of the destroyed or damaged Natanz, Fordow, and Esfahan tunnel facilities and will strike anyone attempting excavation or entry. Tehran would confront major difficulties enriching HEU to WGU, since its four enrichment facilities were destroyed, heavily damaged, or rendered inaccessible. Iran would likely need to build a new covert plant or complete the possible enrichment facility at Pickaxe Mountain near Natanz.

Producing new uranium from scratch would be arduous: Israel eliminated most of Iran’s centrifuge supply chain and destroyed the Ardakan uranium mining and milling facility, while the United States and Israel targeted Esfahan’s conversion capabilities. Jerusalem also targeted Iran’s plutonium route to nuclear weapons during both conflicts.

In addition, Israel degraded Iran’s weaponization pathway during both rounds, striking up to 11 weaponization facilities, the headquarters of Iran’s weaponization program, known as SPND, and eliminating 12 nuclear scientists in June 2025, plus five more facilities and eight scientists in February-April 2026.

As a result, Iran’s path to a nuclear weapon is severely degraded. Any realistic assessment accounting for all these setbacks would place the timeline at two and a half years at least, absent foreign assistance.  

Tehran Must Verifiably Give Up Uranium Enrichment, Weaponization Work

The surest path to ending Tehran’s quest for nuclear weapons is to provide maximum support to the Iranian people as they seek to overthrow the regime that oppresses them.

Diplomatic solutions currently under negotiation remain an option, but any deal with the regime must require Iran to fully and verifiably declare and dismantle its nuclear program while Trump is in office. The regime must also permanently forgo uranium enrichment, plutonium reprocessing, and all weaponization work.

Andrea Stricker is a research fellow and deputy director of the Nonproliferation Program at the Foundation for Defense of Democracies (FDD). For more analysis from the author and FDD, please subscribe HERE. Follow FDD on X @FDD. Follow Andrea on X @StrickerNonpro. FDD is a Washington, DC-based, nonpartisan research institute focused on national security and foreign policy.