The networks targeted are based in several countries including Iran, Hong Kong, China, and Germany, the US Treasury Department says.
The United States has sanctioned an alleged Iranian weapons procurement network supporting the country's ballistic missile programme following the UN decision to reimpose sanctions on Tehran, the Treasury Department announced on Wednesday.
Washington said it was targeting 21 companies and 17 individuals who "pose a significant threat to US service members in the Middle East, US commercial ships transiting international waters, and civilians".
The move, it added, follows the United Nations' September 27 decision to reimpose sanctions and restrictions on Tehran's nuclear, missile, and other armed programmes.
The designations are the first to be imposed by the Trump administration since so-called "snapback" sanctions were finalised last week, which will ramp up the pressure on Tehran over its nuclear weapons and ballistic missile programmes.