U.S. defense analyst Greg Jones gave one of the more urgent warnings this month, arguing that if Iran decides to make a bomb it could produce enough highly-enriched uranium (HEU) in about eight weeks.

“The timeframe will shrink to only about four weeks by the end of next year as Iran’s enriched uranium stockpiles and enrichment capacity continue to increase,” Jones, of the conservative Nonproliferation Policy Education Center, said.

Iran “needs to be treated as a de facto nuclear power simply by virtue of being so close to having a weapon,” he added in an article in U.S. political magazine New Republic.

Other experts say such estimates are unrealistic, given the hurdles Iran must still overcome.