Iran's highest authority Ayatollah Ali Khomenei, said on Monday that Tehran would never yield to international pressure to deprive it of its right to nuclear technology, state radio said.
"The Iranian nation surely will not abandon its right and Iranian officials have no right to deprive the nation of its right," Khomenei was quoted as saying on the occasion of the Shi'ite Muslim feast of Eid al-Ghadir.
Khomenei, who was shown on television, was making his first public appearance since rumours appeared on websites on Thursday that he had died. Iran last week denied the reports.
Khomenei has final say on all state matters in the Islamic Republic, including Iran's nuclear standoff with the West.
The UN Security Council voted unanimously on December 23 to impose sanctions on Iran's trade in sensitive nuclear materials and technology in an attempt to stop uranium enrichment work that could produce material that could be used in bombs.
Iran's President Mahmoud Ahmadinejad has called the resolution a "piece of torn paper" and has vowed to press ahead with Iran's peaceful nuclear program.
The West fears Iran may be pursuing nuclear weapons under cover of a civilian program.