Iran's port authority has said the United Kingdom might free its seized oil tanker after some documents were exchanged that would help secure its release.
British Royal Marines last month stopped and seized the vessel off the shore of Gibraltar on suspicion it carried Iranian crude oil to Syria in breach of European Union sanctions against the government of Syrian President Bashar al-Assad.
"Britain is interested in releasing Iran's oil tanker Grace 1 … following the exchange of some documents, we hope the release will take place soon," Jalal Eslami, the deputy head of Iran's Ports and Maritime Organization, was quoted as saying by the official IRNA news agency on Tuesday.
"The vessel was seized based on false allegations ... it has not been freed yet."
But a senior official in Gibraltar, speaking on condition of anonymity, denied the report, calling it "untrue", according to The Associated Press news agency. Reuters news agency also quoted an unnamed top Gibraltarian government source as saying that that report was not correct.
Earlier on Tuesday, Gibraltar said it was seeking to de-escalate issues arising with Iran since the detention of Grace 1.
"We continue to seek to de-escalate issues arising since the lawful detention of Grace 1," a spokesman for Gibraltar said.
The current detention order on the vessel expires on Saturday night, after which a court is to decide on its fate.
Quoting Gibraltar authorities, the semi-official FARS news agency said the ship will be released by Tuesday evening.
Two weeks after the ship's seizure, Iran's Revolutionary Guard Corps captured a UK-flagged, Sweden-owned, vessel for breaking "international maritime" rules in the Strait of Hormuz.
Tanker traffic through the Strait - where a fifth of the world's oil passes - has become the focus of a standoff between Iran and the US, which has beefed up its military presence in the Gulf since May.
Britain, which repeatedly ruled out any exchange and has since been giving UK-flagged vessels in the region a naval escort, joined a US-led security mission in the narrow passageway on August 5 in order to secure maritime traffic.