Iranian officials have not said where the ship would go, only that its cargo had been sold to an unnamed buyer.
The move prompted renewed speculation that it is heading to Syria.
The "Grace 1" oil tanker became the Adrian Darya 1' under the Iranian flag in mid-August.
Iran and three European countries - Britain, France and Germany - have been trying to save a landmark agreement reached in 2015 and meant to limit Tehran's nuclear programme after the us pulled out a year ago.
President Trump abandoned the accord past year and reimposed sanctions in the fall, violating the terms of the agreement.
Yesterday's meeting between French and Iranian officials was to fine-ten deals of the credit lines. He could not be identified publicly because of the sensitive nature of the subject.
The idea is "to exchange a credit line guaranteed by oil in return for, one, a return to the JCPOA (Iran nuclear deal)...and two, security in the Gulf and the opening of negotiations on regional security and a post-2025 (nuclear program)", Le Drian told reporters. "Symbolically, Iranians prefer to show that Instex isn't working because it allows them to think they can keep the pressure on us".
But Rouhani stressed the Iranian countermeasures were reversible. Moscow would like to have Tehran's opinion of the global community's efforts for preserving the Joint Comprehensive Plan of Action for the Iranian nuclear program, Russian Foreign Minister Sergey Lavrov said in his opening remarks at a meeting with his Iranian counterpart Mohammad Javad Zarif in Moscow on Monday.
A United Nations watchdog has already warned that Iran is already enriching uranium up to 4.5 percent.
Abbas Mousavi, a spokesman for Iran's foreign ministry, told the broadcaster the personnel were being freed on humanitarian grounds and would be allowed to leave the country soon.
Little seems to have come out of those trips.
Jean-Yves le Drian said talks on the credit arrangement, which would be guaranteed by Iranian oil revenues, were continuing, but that United States approval would be crucial, Reuters news agency reported on Tuesday.
But Hook also said that he had not yet seen a "concrete" French proposal.
Europe, he said, needs to compensate Iran in the "amount of $15 billion over a 4-month span" and "after that, Iran is ready for talks".
Iranian President Hassan Rouhani earlier on Wednesday warned that Tehran would continue to scale back its commitments under the historic 2015 deal within the next two days. "Start haggling with the Europeans after you have already taken the third step", the paper advised the Rouhani government, suggesting that more breaches will give Iran the upper hand.