Gibraltar media is reporting that the government has decided to release the Grace 1 Iranian supertanker after receiving formal written assurances from the government in Tehran that it would not discharge its cargo in Syria.
"On that basis, Gibraltar's Chief Minister Fabian Picardo has decided to lift the detention order and allow the ship to sail," the the Gibraltar Chronicle said on Twitter on August 15.
The reported move came despite a last-minute attempt by the United States to seize the vessel at the heart of a standoff between Tehran and London.
"The U.S. Department of Justice has applied to seize the Grace 1 on a number of allegations which are now being considered," the Gibraltar government said in a statement on August 15, adding that the matter will be reviewed by the British overseas territory's Supreme Court at 4 p.m. local time (1400 GMT/UTC).
The U.S. application came "just hours before the Gibraltar government was poised to release" the Iranian supertanker that has been detained since early July.
"...the Government of #Gibraltar has now received formal written assurances from the Iranian government that the ship will not discharge its cargo in #Syria," the newspaper tweeted.
However, it added that "It is not clear at this stage when the ship will sail from #Gibraltar, or whether the U.S. will formally apply to the court to detain it before that happens."
The U.S. Justice Department didn't comment on the matter, while Britain's Foreign Office said the "investigations conducted around the Grace 1 are a matter for the government of Gibraltar."
The current detention order on the Grace 1 is set to expire on the evening of August 17.
On July 4, authorities in Gibraltar seized the vessel with the help of British Royal Marines. The Grace 1 was carrying 2.1 million barrels of Iranian oil and authorities alleged that it was in violation of European Union sanctions on Syria.
Iran says the tanker was in international waters and was not headed to Syria.
In response to the Iranian ship's seizure, Iran's Islamic Revolutionary Guards Corps (IRGC) on July 19 captured the British-flagged oil tanker Stena Impero close to the strategic Strait of Hormuz, which connects the Persian Gulf with the Gulf of Oman.
Tehran said the vessel was "violating international maritime rules," while the British authorities called the seizure "state piracy."
On August 13, the deputy head of Iran's port authority, Jalil Eslami, said that Britain was thinking of freeing the Grace 1 following an exchange of documents.
"We hope the release will take place soon," Eslami said in comments reported by state news agency IRNA.
A spokesman for the Gibraltar government had earlier said it was seeking to "deescalate issues arising since the lawful detention of Grace 1."
The spat between Tehran and London came amid rising tensions in the Persian Gulf after the United States last year withdrew from the 2015 deal between world powers and Tehran.
Washington has appealed to its partners to help create a maritime security mission to help safeguard shipping and other interests in the Persian Gulf.
Earlier, Britain said it was joining the U.S.-initiated task force to escort ships through and around the region, though some other European powers, most notably Germany, have rejected the idea, fearing the United States will use the force as part of its "maximum pressure" campaign against Iran.
The captain and three officers from the Grace 1 have already been released from arrest.
The legal team for the captain, chief officer, and a third crew member of the Grace 1 told the BBC that formal police proceedings against them had ended.