DUBAI and ABU DHABI — Iran's Revolutionary Guard Corps and its external Quds Force are still moving oil worth hundreds of millions of dollars through sprawling illicit shipping networks, despite a maximum pressure sanctions regime from Washington and scores of corporate and government entities blacklisted. Washington is working to crack down on this, the U.S. Treasury Department says, and it's warning those in the maritime industry to be wary of involvement with regimes or entities that have been deemed terror sponsors by the U.S. — or face steep costs. Sigal Mandelker, under secretary for terrorism and financial intelligence at the U.S. Treasury Department, spoke to CNBC's Hadley Gamble during a visit to Abu Dhabi. "What we're doing on this trip and really every day is we're telling the maritime industry that they need to be on high alert, they need to continue to sophisticate their ability to track vessels that are involved with any of these regimes," Mandelker said. "Whether it's Iran, Venezuela or North Korea, no one should want to have anything to do with funding regimes engaged in this kind of activity." The conversation came just days after the Treasury Department's Office of Foreign Assets Control (OFAC) moved to designate 37 entities allegedly tied to Iran's Quds Force under Executive Order 13224. The order, first enacted under the Bush administration after the September 11, 2001 attacks, classifies relevant actors as specially designated global terrorists (SDGT) and gives the State Department and Treasury authorization to block their U.S. assets, prohibit Americans from transacting with them, and coordinate with other countries to cut off their funding sources.

"To anyone considering manning one of these vessels... there will be real consequences to them if they continue." Sigal Mandelker Under Secretary for Terrorism and Financial Intelligence, U.S. Treasury Department

Those designated last week include 16 entities, 10 individuals and 11 vessels which OFAC says were involved in illicit maritime trade linked to terrorism funding. Anyone owning or operating any of the designated vessels, any company that fuels them, and any port that allows them entry is also subject to U.S. sanctions. "In this action, for example, we've exposed that this is an oil-for-terror network going to the Quds Force and Hezbollah, and no one in the world should have anything to do with that kind of network," Mandelker said. "And here we've also sanctioned the captain. That should send a strong deterrent message to anyone considering manning one of these vessels that there will be real consequences to them if they continue." OFAC also warns of sanctions risks related to oil shipments to Syria, many of which come from Iran, tanker tracking data has shown.

The U.S. has long designated the Iranian-sponsored Lebanese militant group Hezbollah as an SDGT under the order, and more recently brought Iran's Islamic Revolutionary Guard Corps into that group, the first time a government entity has been so designated -- leading Iran to in turn brand all U.S. military personnel in the Middle East as terrorists. Tehran rejects the U.S. designation, and has called Washington's sanctions "economic terrorism."

Ghost ships and the Adrian Darya 1