The ship, formerly called Grace 1, was detained by Britain off Gibraltar in July.

The U.S. Treasury Department on Friday blacklisted the Iranian oil tanker Adrian Darya, which is at the center of a confrontation between Washington and Tehran, and sanctioned its captain.

The ship, formerly called Grace 1, was detained by Britain off Gibraltar in July due to British suspicion it was carrying Iranian oil to Syria in violation of European Union sanctions. It was released in mid-August after Iran gave assurances its cargo was not headed to Syria.

"Vessels like the Adrian Darya 1 enable the (Islamic Revolutionary Guard Corps-Quds Force) to ship and transfer large volumes of oil, which they attempt to mask and sell illicitly to fund the regime's malign activities and propagate terrorism," Treasury Under Secretary Sigal Mandelker said in a statement.

"Anyone providing support to the Adrian Darya 1 risks being sanctioned," she said.

The United States considers Iran's Revolutionary Guard Corps a terrorist group.

Turkey said on Friday the ship was headed to Lebanon's waters after changing course several times, although Beirut said it was not informed of the plan. It raises the possibility that a ship-to-ship transfer of cargo may be attempted once it nears Lebanon's coast.