The Institute for Science and International Security did not make a judgment on whether Iran plans to turn its enrichment capabilities toward weapons making. But in its report made available to The Associated Press ahead of publication Monday, it drew a clear distinction between Tehran’s ability to make the fissile core of warhead by producing 25 kilograms (55 pounds) weapons-grade uranium from its lower enriched stockpiles and the warhead itself.

“Despite work it may have done in the past,” Iran would need “many additional months to manufacture a nuclear device suitable for underground testing and even longer to make a reliable warhead for a ballistic missile,” the report said.

Additionally, ISIS — which often advises Congress and other branches of U.S. government on Iran’s nuclear program — said any attempt to “break out” into weapons-grade uranium enrichment would be quickly detected by the United States and the International Atomic Energy, which monitors Tehran’s known enrichment sites. With Washington likely to “respond forcefully to any “break-out” attempt, Iran is unlikely to take such a risk “during the next year or so,” said the report.