An Iranian supertanker detained in Gibraltar has been released by authorities in the British Overseas Territory.
The Grace 1 was seized last month in a British Royal Navy operation off Gibraltar.
The vessel was suspected of violating European Union sanctions on oil shipments to Syria.
The Supreme Court in Gibraltar had delayed a decision to release the Grace 1 after the US Department of Justice made an application to extend the vessel's detention, the Gibraltar government said earlier on Thursday.
The detention of the Grace 1 last month saw Iran later seize the British-flagged oil tanker Stena Impero, which remains held by the Islamic Republic.
Analysts had hoped the release of the Grace 1 by Gibraltar would see the Stena Impero similarly released.
Lina Khatib, head of the Middle East and North Africa programme at Chatham House, said the US request on the Grace 1 was based on its own imposed sanctions on Iran, and not the EU's sanctions on oil exports to Syria.
"Although the US expects its European allies to abide by these sanctions, it is up to the Gibraltar authorities to assess the allegations presented by the US," Ms Khatib said.
The US has been asking its allies to take part in a naval mission to protect shipping in the strategic Strait of Hormuz, at the mouth of the Persian Gulf, though European nations have been reluctant.
Britain has so far been the only one to express willingness to join a maritime security mission. It has also been giving UK-flagged vessels a naval escort since the Iranian Revolutionary Guard's seizure of the Stena Impero.
A Foreign and Commonwealth Office spokesperson said:
"The UK notes the conclusion of Gibraltar's legal proceedings and the steps Gibraltar's authorities have taken to prevent the ship's cargo from reaching Syria in contravention of EU Syria Sanctions.
"We note the Government of Gibraltar has received assurances from Iran that the Grace 1 will not proceed to Syria.
"Iran must abide by the assurances they have provided.
"We will not stand by and allow Iran - or anyone - to bypass vital EU sanctions on a regime that has deployed chemical weapons against its own people.
"There is no comparison or linkage between Iran's unacceptable and illegal seizure of, and attacks on, commercial shipping vessels in the Strait of Hormuz and the enforcement of EU Syria sanctions by the Government of Gibraltar. Freedom of navigation for commercial shipping must be respected and international law upheld."