The State Department on Wednesday refused to concede that Iran violated its nuclear agreement with the U.S. and other countries by stockpiling more heavy water than allowed under the deal.

The International Atomic Energy Agency concluded that Iran had stockpiled heavy water, a material needed for nuclear reactors, at a level that exceeds the amount they’re allowed to maintain under the terms of the deal. The IAEA made that determination in a Nov. 2 report, which Reuters revealed on Wednesday.