An Iranian oil tanker at the center of a standoff among the United States, the United Kingdom, and Iran left the territorial waters of Gibraltar on Sunday despite a request from the U.S. to detain the ship. The tanker has become central to the rising tensions between the West and Iran since British and Gibraltar authorities seized the ship on July 4, believing it was transporting oil to Syria, a violation of European Union sanctions. Iran denied that the ship was intended for Syria and, two weeks later, seized a British tanker. The seizure by Iran was widely viewed as retaliatory. On Friday, the Justice Department unsealed a warrant instructing the U.S. to seize the Iranian tanker. However, the government of Gibraltar rejected the American warrant on Sunday, stating that it relied on U.S. sanctions against Iran that were not applicable in the European Union. Gibraltar’s rejection of the American request leaves questions as to how the U.S. will respond. The ship’s next destination is unknown.