The episode began Monday night when the U.S. Navy observed an Iranian ship towing the Saildrone Explorer, an unmanned U.S. vessel equipped with camera, radars and sensors.
The USS Thunderbolt, a patrol coastal ship, and a Navy helicopter moved toward the scene. The Iranians dropped the tow line and eventually left the area, the defense officials said.
No shots were fired by either side, the defense officials added, and the Americans didn’t try to prevent the Iranian ship, which was operated by Iran’s Islamic Revolutionary Guard Corps, from leaving.
Vice Adm. Brad Cooper, the commander of the U.S. naval forces in the region, said the Iranian actions, which took place in international waters, were “flagrant, unwarranted and inconsistent with the behavior of a professional maritime force.”