An American-owned oil tanker long suspected of carrying sanctioned Iranian crude oil began offloading its cargo near Texas late Saturday, tracking data showed, even as Tehran has threatened to target shipping in the Persian Gulf over it.

Ship-tracking data analyzed by The Associated Press showed the Marshall Islands-flagged Suez Rajan was undergoing a ship-to-ship transfer of its oil to another tanker, the MR Euphrates, near Galveston, some 70 kilometers (45 miles) southeast of Houston.

The fate of the cargo aboard the Suez Rajan has become mired in the wider tensions between the U.S. and the Islamic Republic, even as Tehran and Washington work toward a trade of billions of dollars in frozen Iranian assets in South Korea for the release of five Iranian-Americans held in Tehran. Iran has been trying to evade sanctions and continue selling its oil abroad, while the U.S. and its allies have been seizing cargoes since 2019 after the country’s nuclear deal allowing the trade collapsed.

Already, Iran’s paramilitary Revolutionary Guard has warned that those involved in offloading the Suez Rajan’s cargo “should expect to be struck back.” The U.S. Navy has increased its presence steadily in recent weeks in the Mideast, sending the troop-and-aircraft-carrying USS Bataan through the Strait of Hormuz in recent days and considering putting armed personnel on commercial ships traveling through the strait to stop Iran from seizing additional ships.