The UK would ensure the release of a seized Iranian tanker if Tehran guaranteed the oil was not going to Syria, Jeremy Hunt, the foreign secretary, has said.

Mr Hunt revealed he had made the suggestion to his counterpart in Iran, Javad Zarif.

Mr Zarif insisted Iran also wanted to resolve the stand-off, he said.

British Royal Marines impounded the supertanker Grace I off the coast of Gibraltar last week on suspicion of violating EU sanctions by taking crude oil to Syria.

Iran, which denies transporting oil to Syria, has demanded that Britain release the vessel.

Tensions high as Trump approves new Iran sanctions: In pictures Show all 17 1 /17 Tensions high as Trump approves new Iran sanctions: In pictures Tensions high as Trump approves new Iran sanctions: In pictures Iran claims that in this picture released by Iran state TV, their surface-to-air missile is seen as it shoots down a US surveillance drone EPA Tensions high as Trump approves new Iran sanctions: In pictures This photo shows US RQ-4A Global Hawk unmanned surveillance drone. A drone of this model was shot down by Iran on Thursday 21 June AFP/Getty Tensions high as Trump approves new Iran sanctions: In pictures An oil tanker is on fire after it was subject to a suspected attacked at the Gulf of Oman on June 13. The US has blamed Iran for the attack Reuters Tensions high as Trump approves new Iran sanctions: In pictures Iran claims that in this picture released by Iran state TV, debris from the downed US drone is seen after it was recovered from Iranian waters AFP/Getty Tensions high as Trump approves new Iran sanctions: In pictures Smoke billows from an oil tanker after it was subject to a suspected attacked at the Gulf of Oman on June 13 Reuters Tensions high as Trump approves new Iran sanctions: In pictures US President Trump holds up a signed executive order to increase sanctions on Iran on 24 June AP Tensions high as Trump approves new Iran sanctions: In pictures Iranian President Rouhani stated in a televised address that the White House is "afflicted by mental retardation" following the increase in sanctions on 25 June EPA Tensions high as Trump approves new Iran sanctions: In pictures An Iranian navy boat tackles the fire on the Norwegian owned Front Altair oil tanker after it was hit in a suspected attack AFP/Getty Tensions high as Trump approves new Iran sanctions: In pictures Iran claims that in this picture released by Iran state TV, debris from the downed US drone is seen after it was recovered from Iranian waters AFP/Getty Tensions high as Trump approves new Iran sanctions: In pictures Smoke billows from an oil tanker after it was subject to a suspected attacked at the Gulf of Oman on June 13 Reuters Tensions high as Trump approves new Iran sanctions: In pictures A screenshot from a video released by the US Department of Defense that the US claims to show Iranian removing an unexploded limpet mine form the hull of the Japan-owned ship that was attacked in the Gulf of Oman on June 13 Getty Tensions high as Trump approves new Iran sanctions: In pictures An item reportedly found on the Japan-owned oil tanker that was attacked on June 13 in the Gulf of Oman AFP/Getty Tensions high as Trump approves new Iran sanctions: In pictures A handout photograph from the US Department of Defense shows a composite material that the US claim was left behind on the hull of the Japan-owned oil tanker following the removal of an unexploded limpet mine Getty Tensions high as Trump approves new Iran sanctions: In pictures A view from the cabin of an Iranian navy boat as it tackles the fire on the Norwegian owned Front Altair oil tanker after it was hit in a suspected attack EPA Tensions high as Trump approves new Iran sanctions: In pictures Release by US government A picture released by U.S. Central Command shows damage to the hull of the oil tanker Kokuka Courageous. The picture suggests that the ship is 'likely' to have been hit by a mine as the US Secretary of State Mike Pompeo moves to blame Iran for the suspected attack Reuters Tensions high as Trump approves new Iran sanctions: In pictures Smoke billows from an oil tanker after it was subject to a suspected attacked at the Gulf of Oman on June 13 Reuters Tensions high as Trump approves new Iran sanctions: In pictures Release by US government A picture released by U.S. Central Command shows damage to the hull of the oil tanker Kokuka Courageous. The pictures suggests that the ship is 'likely' to have been hit by a mine as the US Secretary of State Mike Pompeo moves to blame Iran for the suspected attack EPA

The clash has led to an increase in tension in the Gulf, with Iranian boats days later trying to impede a British oil tanker before being seen off by a Royal Navy frigate in the Strait of Hormuz.

The UK is sending a second warship, the destroyer HMS Duncan, to the region to protect British commercial oil tankers.

Mr Hunt tweeted that he had had a constructive call with Mr Zarif and that he reassured his Iranian counterpart the UK’s concern was the destination not the origin of the oil.

The Tory leadership contender added in an interview: “I made clear that we want to resolve the situation with the Grace I tanker in Gibraltar.

“Our concern has always been the destination of the tanker and the fact that it was taking oil to Syria, not the origin of the oil, and I said that if we could receive sufficient guarantees that that tanker was not headed for Syria, then we would be able to resolve the situation, following of course due process in the Gibraltar courts.

“It was a constructive call. Foreign minister Zarif reassured me that Iran too wanted to resolve the situation, and I’ve also spoken to the chief minister of Gibraltar Fabian Picardo, and they are working very closely with us to try and resolve the situation.”

European countries have had sanctions against Iran’s ally Syria since 2011.

Police in Gibraltar said on Thursday they had arrested the captain and chief officer of the supertanker, which Mr Picardo said was carrying 2.1 million barrels of light crude oil, and seized documents.

Tehran claims the US arranged to have its tanker seized after Washington imposed sanctions on Iran with the aim of halting the country’s oil exports.