President Mahmoud Ahmadinejad said on Tuesday that Iran would press ahead with its nuclear plans and that a UN resolution imposing sanctions on Iran was "invalid".
"The Iranian nation is wise and will stick to its nuclear work and is ready to defend it completely," Ahmadinejad said in a televised speech to a rally in the southern city of Ahvaz.
"The UN resolution against Iran's atomic work has no validity for Iranians."
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.
Ahmadinejad said "bullying powers" could not deprive Iran of its right to nuclear technology.
"If bullying powers ... want to resist Iranians' will, we will give them a historic slap in the face," he said, accompanied by chants from the crowd of "Death to America".
Iran, the world's fourth largest oil exporter, insists it wants to produce fuel for nuclear power plants and dismisses charges it is trying to produce nuclear weapons.
Iran's parliament passed a bill on Wednesday obliging the government to revise its level of cooperation with the International Atomic Energy Agency in reaction to the resolution.
Iran's Supreme Leader Ayatollah Ali Khamenei has the final say in nuclear and other matters.
But, like Ahmadinejad, he has insisted Iran will not give up its atomic plans.