Iran says the US has "crossed a red line" by imposing sanctions on the head of its judiciary, Ayatollah Sadeq Amoli-Larijani.
The foreign ministry vowed to retaliate, but did not say what form any action might take.
Iran also rejected any changes to its nuclear deal with world powers.
US President Donald Trump, a critic of the 2015 accord, said on Friday he would extend sanctions relief over the landmark deal one last time.
At the same time the US imposed fresh sanctions on 14 individuals and entities over alleged rights abuses.
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