A senior official in Gibraltar has denied reports that an Iranian tanker seized near the British overseas territory will be released.
The official said a report by Iran's semi-official Fars news agency that the Grace 1 tanker is leaving on Tuesday night are "untrue".
A court in Gibraltar is to decide the fate of the ship on Thursday, when an order for its detention lapses.
Relations between Britain and Iran have been tested since Gibraltar, a British overseas territory, seized an Iranian oil tanker on 4 July.
Royal Marines boarded the Panamanian-registered Grace 1 after it was believed to be breaching EU sanctions whilst on its way to Syria.
The ship was carrying 2 million barrels of crude oil to the Banias Refinery in Syria.
Local police arrested the captain and chief officer of the supertanker.
It came hours after Type 23 frigate HMS Montrose had been forced to intervene when three Iranian fast patrols attempted to "impede" the passage of the BP-operated tanker British Heritage.
Then, British-flagged oil tanker Stena Impero was seized on 19 July in the Strait of Hormuz.
Its crew remains in detention.
Iranian officials said the seizure was in retaliation for the seizure of the Grace 1.
On Thursday, a court in Gibraltar is to decide the fate of the Grace 1, when an order for its detention lapses.
The deputy head of Iran's port authority, Jalil Eslami, said in a report by state news agency IRNA that Britain had shown an interest in overcoming the problem and documents had been exchanged.
"Efforts from Iran and the port organisation have been made for the release of this ship," he was quoted as saying.
"I hope this problem will be resolved in the near future and that the ship can continue its movement with the flag of the Islamic Republic of Iran."