A statement issued by current EU president Austria said the bloc "urges Iran not to take this step which would violate both the letter and the spirit of the eight previous resolutions."
"The EU regrets that Iran has chosen to announce this unilateral move at a moment when international confidence in the peaceful nature of its programme is far from restored," it added.
"It finds it surprising and unreasonable that Iran proposes to do this at a moment when … Britain, France and Germany with the EU were exploring with Iran the possibility of a return to negotiations.
"Resumption of activities and such disregard for the repeated wishes of the IAEA Board of Governors can only seriously jeopardise the possibility of a return to negotiations."
Despite the warning, a senior Iranian nuclear official confirmed Saturday that Tehran will end its more than two year suspension of nuclear fuel research Monday or Tuesday by removing seals on equipment in the presence of AIEA inspectors.
The announcement of the research resumption sparked a warning from the United States that it was ready to seek the referral of Iran’s nuclear programme to the UN Security Council for enforcement action.
Washington charges that the programme is a cover for weapons development, an accusation Tehran strongly denies.