Iran says power lines to its primary underground nuclear facility at Fordo were cut last month by explosive blasts set off by "terrorists and saboteurs."
The head of Iran's atomic agency, Fereydoun Abbasi-Davani, made the comments Monday at a meeting in Vienna of the United Nations atomic watchdog member states. He did not say who was responsible.
Iran has in the past blamed the United States and Israel for targeting its nuclear program and scientists.
The Iranian comments come as European Union foreign policy chief Catherine Ashton said she will meet Iran's chief nuclear negotiator Saeed Jalili in Istanbul on Tuesday. She said the meeting is "part of continuing efforts to engage with Iran."
Talks between world powers and Iran in Moscow in June failed to reach a breakthrough. But German Chancellor Angela Merkel said Monday that a political solution is still possible.
Russia said Monday that ministers from six world powers plan to meet with Iranian negotiators on the sidelines of the U.N. General Assembly meeting next week.
Iran's Abbasi-Davani is expected Monday to meet with with U.N. nuclear inspection chief Yukiya Amano in further negotiations.
Iran is under international sanctions for its controversial nuclear program. Tehran says its program is peaceful while Western nations, Israel and U.N. nuclear experts have expressed fears that Iran is working towards development of a nuclear weapon.
Increased uranium enrichment activity at the Fordo site has raised concerns because it can be a step in weapon development. Iran says the increased enrichment is for medical and energy needs.
The site is dug deep into a mountain, making threatened air strikes by Israel or the United States more difficult.
Meanwhile, the United States and allied nations in recent days began a naval exercise in the Persian Gulf to show their will to keep oil shipping lanes open if Iran retaliates for an Israeli air strike.