Washington and Tehran severed formal diplomatic relations following the Iranian hostage crisis in 1979.
The State Department updated its travel warning Wednesday, calling on U.S. citizens to "carefully consider" the risks associated with traveling to Iran.
"Some elements in Iran remain hostile to the United States," the travel warning reads. "As a result, American citizens may be subject to harassment or arrest while traveling or residing in Iran."
The State Department cautions that several Iranian-American citizens were arrested since 2009, with some held in detention inside Iran for several months.
"Americans of Iranian origin should consider the risk of being targeted by authorities before planning travel to Iran," the warning added.
Meanwhile, the State Department said minority Kurds, Bahais, Arabs and Azeris are at risk of repression inside Iran, singling out the provinces near the border with Pakistan and Afghanistan as particularly unsafe.
Tehran blames Washington for a litany of offenses, including plotting a soft coup in the wake of June political demonstrations and supporting Iranian opposition groups.