Supreme Leader Ayatollah Ali Khamenei, speaking three days before Iran's chief nuclear negotiator is due to meet European Union foreign policy chief Javier Solana in Geneva, also said the Islamic Republic would cut off the hand of any aggressor.
Iran is embroiled in a deepening international standoff over its nuclear programme, which the United States and Israel suspect is aimed at making bombs, a charge Tehran denies.
Six world powers last month offered Iran economic and other incentives to try to persuade it to halt uranium enrichment, which can have both civilian and military uses.
Iranian officials have repeatedly refused to suspend activity which can provide fuel for nuclear power plants but also material for weapons if enriched much more.
Iran, the world's fourth-largest oil exporter, says its nuclear programme is solely aimed at generating electricity.
"This (nuclear) achievement belongs to all the Iranian nation and no power would be able to deprive the Iranian nation of this technology and certain right," Khamenei said.
"In relation to negotiations … we have very clearly defined red lines," he said in a speech quoted by state radio.
Iranian officials have previously said uranium enrichment was a "red line" and would continue.
The standoff over Iran's nuclear activities has sparked speculation of a military confrontation with the United States or Israel and helped push up oil prices to record levels.
Iran has vowed to strike back at Tel Aviv, as well as U.S. interests and shipping, if it is attacked.
"The hand that would attack the Islamic Republic of Iran will be cut off," Khamenei said. (Reporting by Hashem Kalantari; Writing by Fredrik Dahl; Editing by Giles Elgood)
