New EU sanctions to come into effect against Iran on Sunday will hurt negotiations over the country's nuclear programme, foreign ministry spokesman Ramin Mehmanparast said.
"Actions that are against the agreements between Iran and the P5+1 will have a negative impact on reaching an acceptable resolution," he told reporters on Tuesday in his regular weekly briefing.
Iran and the P5+1 -- permanent UN Security Council members the United States, Britain, France, China and Russia, plus Germany -- this year revived talks over Tehran's disputed atomic activities, but they are making little progress.
After three inconclusive rounds, the talks have been downgraded to experts level, with the next meeting scheduled for July 3 in Istanbul.
That is two days after the European Union fully implements an embargo on Iranian oil.
The phasing in of the embargo over the past five months has cut Iran's crude sales by 40 percent, according to the International Energy Agency.
Iranian officials dispute that and say the embargo will have little effect and hurt only faltering EU economies.
"Taking measures against our national interests (by the EU) will depict a negative image of hostility towards our nation," Mehmanparast said. "It is better that European officials think about their internal issues."
He added that the sanctions would only be "damaging" for EU-Iran relations.
"As well as possible impacts on the negotiations (with the P5+1), sanctions will intensify the economic and social problems in European countries," he said.