The warning came from David Peyman, the deputy assistant Secretary of State for counter threat finance and sanctions, on Monday.

Namely, Peyman said the US will encourage ship captains to take photos of anyone conducting STS transfers of sanctioned oil and submit them to the US government.

In addition, he said the advisories will warn shipping vessels against turning off AIS in an effort to avoid US sanctions on Iran.

IMO requires vessels to use transponders for safety, which can be turned off in cases of piracy or similar hazards.

However, a global wave of sanctions has triggered tactics such as shutting off AIS in order to conceal a ship's illicit activities.

Trump pulled out of the Iran nuclear deal in 2018, therefore reimposing sanctions on Iran’s oil exports.

Meanwhile, Iran says its nuclear program is for peaceful purposes.

The Trump administration imposed sanctions in September on units of COSCO for transporting the blacklisted crude.