The Trump administration announced new sanctions aimed at Iran‘s “shadow fleet” of oil tankers that it said are used to fund destabilizing activities around the world. The sanctions, imposed Monday by the Treasury Department’s Office of Foreign Assets Control and the State Department,

The U.S. Treasury and the U.S. State departments sanctioned more than 30 people and ships, including the heads of Iran’s National Iranian Oil Co., and the Iranian Oil Terminals Co., for their role in brokering the sale and transportation of Iranian oil.

The Trump administration imposed a new round of sanctions on oil brokers, ships and people it said were linked to illicit shipments of Iranian crude, framing the move as a return to a “maximum pressure” strategy to squeeze the country’s economy.