US slaps sanctions on Iran supreme leader's aides
"This action further constricts the supreme leader's ability to execute his agenda of terror and oppression," Treasury Secretary Steven Mnuchin said in a statement.
The move comes as thousands rallied outside the former US embassy in Tehran on Monday to mark the 40th anniversary of the Iran hostage crisis.
On 4 November 1979 less than nine months after the toppling of Iran's American-backed shah, students overran the embassy complex to demand the United States hand over the ousted ruler after he was admitted to a US hospital.
It took 444 days for the crisis to end with the release of 52 Americans, but the US broke off diplomatic relations with Iran in 1980 and ties have been frozen ever since.
The 40th anniversary comes at a time of escalating tensions between Tehran and Washington and also the region.