Dubai, Sept. 1 -- An Iranian oil tanker pursued by the U.S. across the Mediterranean Sea slowed to a near-stop Sunday off the coast of Syria, where America's top diplomat alleges it will be unloaded despite denials from Tehran.

The ongoing saga of the Adrian Darya 1, formerly known as the Grace 1, comes as tensions remain high between the U.S. and Iran over its unraveling nuclear deal with world powers. Tehran is set to send a deputy foreign minister and a team of economists to Paris on Monday for talks over ways to salvage the accord after a call between Iranian President Hassan Rouhani and French President Emmanuel Macron.

The ship-tracking website MarineTraffic.com showed the Adrian Darya slowed to a near-stop on Sunday some 50 nauti...