The United States has warned mariners around the world not to work with any vessel associated with Iran’s Revolutionary Guards, or IRGC, threatening “serious consequences”.

A statement issued by the State Department spokesperson Morgan Ortagus August 15 says, “The IRGC has been designated a Foreign Terrorist Organization (FTO) by the United States. Crewmembers of vessels assisting the IRGC by transporting oil from Iran may be ineligible for visas or admission to the United States”.

In the statement the case of the Iranian supertanker Grace-1, which was detained by Gibraltar on July 4 is mentioned as an example of a vessel transporting Iranian oil to Syria.

The statement adds, “The maritime community should be aware that the U.S. government intends to revoke visas held by members of such crews. In the case of the M/T Grace I, we will continue to act consistent with our existing policies concerning those who provide material support to the IRGC.”

Secretary of State Mike Pompeo has also tweeted the statement saying, “A message to all mariners – if you crew an IRGC or other FTO-affiliated ship, you jeopardize future entry to the U.S.”

Gibraltar freed the detained tanker on August 15, at the same time reports began circulating that the U.S. is petitioning the British territory to impound the ship.