At present Iran has been enriching uranium only to 3.5 percent, the level needed for use in its Bushehr nuclear power plant. The Tehran medical reactor will require 20 percent enriched uranium, a significant increase but still well short of the levels needed for weapons.
Ahmadinejad ordered the production to begin but officials have not yet given a date. Iran’s state media reports that Iran is running out of medical isotopes, which forced the decision, but officials still say they hold out hope for a third party enrichment deal.
Western officials are widely expected to use the increase in enrichment levels as an excuse to press for additional sanctions against Iran. Since Western officials were already pushing for more sanctions before the announcement, however, it is unclear if it will have any practical effect.