State Department spokesperson Tommy Pigott said the measures aim to curb Iran's use of oil revenues to "fund destabilising activities around the world and step up its repression inside Iran."
The sanctions also target 15 entities and two individuals.
President Donald Trump reaffirmed his commitment to "driving down the Iranian regime's illicit oil and petrochemical exports" under the administration’s maximum pressure campaign.
The talks in Oman, described by Iran’s foreign minister as having a "positive atmosphere," focused on Iran's nuclear program.
The discussions come amid heightened tensions following violent crackdowns on protests in Iran and Trump’s prior threats of military action.
Since Trump’s first term, the US has repeatedly imposed sanctions to pressure other nations to halt Iranian oil purchases.