The Iranian supertanker seized off the coast of Gibraltar last month is expected to leave the British overseas territory tonight.
Hamid Baeidinejad, Iran's ambassador to the UK, revealed on Twitter that the vessel would be leaving, although did not specify a time.
It is unclear where the boat, which was arrested for allegedly attempting to break EU sanctions by delivering oil to Syria, will now head.
Gibraltar rejected a renewed request from the US to not release the Grace 1, which has now been renamed Adrian Darya.
On Thursday, Gibraltar announced that the vessel was free to leave after it was seized more than a month ago.
The US issued a warrant on Friday to seize the vessel, a day after Gibraltar lifted the ship's detention.
It is currently still at anchor off the coast of Gibraltar, along with the 2.1 million barrels of oil it was accused of trying to deliver to Syria.
The detention of the Grace 1 saw Iran later seize the British-flagged oil tanker Stena Impero, which remains held by the Islamic Republic.
The Grace 1’s release comes after the US under President Donald Trump pulled out of Iran’s nuclear deal with world powers over a year ago, setting in motion a growing confrontation between Tehran and the West over its atomic programme.
Reacting to the latest developments, Iran’s foreign minister Mohammad Javad Zarif accused the US of trying to “steal our property on the high seas”.
He tweeted: “Having failed to accomplish its objectives through its #EconomicTerrorism — including depriving cancer patients of medicine — the US attempted to abuse the legal system to steal our property on the high seas,” and he described the Trump administration’s moves as a “piracy attempt”.
In recent weeks, the Persian Gulf region has seen six attacks on oil tankers that the US has blamed on Iran and the downing of an American surveillance drone by Iranian forces. Iran has denied being behind the tanker attacks, though it has seized other vessels.