The authorities of Gibraltar ruled earlier on Thursday to release the tanker, which was captured on 4 July on suspicion of transporting oil to Syria in alleged violation of EU sanctions, Trend reports citing Sputnik.

Spokesperson for the US Department of State Morgan Ortagus claimed in a statement on Thursday, that Grace 1 "was assisting the Islamic Revolutionary Guard Corps (IRGC) by transporting oil from Iran to Syria" and this "could result in serious consequences for any individuals associated with the Grace 1". Ortagus warned that the US "intends to revoke visas held by members of such crews".

According to the Gibraltar Chronicle newspaper, the US Department of Justice sought to seize Grace 1 mere hours before Gibraltar was poised to set it free. The vessel, however, was still released, albeit a few hours after the supertanker’s captain and three crew members were freed.

Iranian Foreign Minister Javad Zarif has slammed the United States’ move as a "piracy attempt".