Iran must reverse its decision to enrich uranium at higher levels and give international diplomacy a chance to save the 2015 nuclear accord, the European Union said in a statement.
"The initiation of uranium enrichment to up to 20% by Iran at the underground Fordow Fuel Enrichment Plant ... is a very serious development and a matter of deep concern," the EU's 27 governments said in a statement released late on Monday.
"At this critical juncture, Iran's action also risks undermining efforts aimed at building upon the existing diplomatic process. We urge Iran to refrain from further escalation and reverse this course of action without delay."