Confusion on whether Iran truly needed only “two weeks to four weeks” to make a nuclear weapon, as President Donald Trump suggested on Monday, hangs over the ongoing U.S. and Israeli war on the Persian Gulf nation. Nuclear experts call this claim unlikely—but the confusion may stem from some basics of atomic chemistry.
“There was no evidence that Iran was close to a nuclear weapon,” says Jeffrey Lewis of the James Martin Center for Nonproliferation Studies at the Middlebury Institute of International Studies. His comment echoed those of other experts after the war’s start, as well as statements from International Atomic Energy Agency (IAEA) chief Rafael Grossi at that time and in 2025 and last year’s “threat assessment” report by U.S. intelligence agencies.
According to an IAEA estimate, as of June 2025, Iran possessed 441 kilograms of 60 percent enriched uranium, where the percentage refers to the share of the isotope uranium 235 (U 235) found in the material. That would be enough for 10 nuclear weapons if the material could be enriched further to full 90 percent weapons-grade concentrations, according to the IAEA. That further enrichment would take a matter of weeks in a fully functioning Iranian nuclear complex, perhaps explaining the time line within Trump’s declaration.