Iran's Foreign ministry spokesman Abbas Mousavi has told state television the "necessary steps" to set the Swedish-owned ship free were "underway".
"The final steps of the legal procedure are underway and, God willing, the boat will be released in the coming days," he said, without giving further details.
Iran's Islamic Revolutionary Guard Corps seized the Stena Impero on July 19 in the Strait of Hormuz with 23 crew members on board, claiming it broke "international maritime rules".
On Wednesday, the Swedish foreign ministry said that some of the crew had been released, after the vessel's owners said they expected seven to be set free on that day.
The seizure of the tanker was seen as a tit-for-tat move after British authorities detained an Iranian tanker off Gibraltar in July on suspicion it was shipping oil to Syria in breach of EU sanctions.
Gibraltar released the ship - formerly called the Grace 1 but since renamed the Adrian Darya 1 - on August 18 after receiving written assurances from Iran that it would not head to countries under EU sanctions.
Tehran denied it had made any promises about the destination of the ship laden with 2.1 million barrels of oil, which had been elusive since leaving Gibraltar .
On Sunday, Mousavi said the Adrian Darya "has reached its destination and the oil has been sold", without providing further details.
Mousavi did not specify if the Adrian Darya had unloaded its cargo.
"It is in the Mediterranean," he said, facing the coast of a country he did not name.
Iran last month said it had "sold the oil" aboard the tanker and that the owner will decide the destination, but it did not identify the buyer.
Maritime tracking service TankerTrackers said that as of Sunday night the Adrian Darya was off the coast of Syria's Tartus but had not unloaded the oil.
Tensions between arch-enemies Iran and the US have soared ever since Washington stepped up its campaign of "maximum pressure" against Tehran
The US has re-imposed sanctions after scrapping the landmark 2015 nuclear deal last year.
