Iran war negotiations are putting the country’s uranium enrichment program back under scrutiny. U.S. President Donald Trump has said preventing Iran from building a nuclear weapon is a main war objective. Iran’s leaders insist the program is for peaceful purposes. Uranium is found in slightly different configurations. One is best at powering nuclear reactions. A process called enrichment isolates the more desirable U-235 from its more stable cousin. This takes anywhere from days to months to years. Before the war, Iran had a stockpile of enriched uranium that was a short, technical step from weapons-grade material. Tehran hasn’t allowed regulatory agencies access to its nuclear facilities bombed by Israel and the United States during the June 2025 12-day war.