More than 40 years after the war over the territory, sovereignty of the archipelago in the south-west Atlantic Ocean remains hotly disputed between Britain and Argentina.

However in a 2013 referendum, residents of the islands voted overwhelmingly to remain a British overseas territory – with 99.8% voting in favour and just three voting against.

When asked about if the Prime Minister believed the UK had the necessary forces to defend the sovereignty of the islands the spokesperson said the they will remain so far as long as the islanders wish”.

“Our armed forces are on standby 24/7 to protect the UK and our interests”, the spokesperson added.

Announcing his plan for sanctions in a national address on Thursday, Milei reiterated that the Falkland Islands were “historically and legally” Argentinian.

He said: “There can be no argument. They are part of the Argentine territory.

“The islanders on their usurped territory do not have a legitimate right to self-determination and any argument on any such self-determination is invalid.”

Milei described the Sea Lion oilfield as a “clear and present danger”, and said if Argentina does not act swiftly, “they will have the material capacity to access the oil that lies underneath our sea – something that has never happened before.”

He continued: “The Falklands are our future, we need to recover these islands which are nationally relevant. There is no other path forward”.

It is not yet clear how or to what extent the sanctions will be imposed or tightened. In Argentina, a current law already allows for restrictions of activities of oil companies participating in projects considered unauthorised on the islands.

Two oil companies – Britain’s Rockhopper Exploration and Israel’s Navitas Petroleum – are due to begin extracting oil in the Sea Lion oilfield off the Falklands coast within two years, something Milei said Argentina could not allow.

A joint statement from the two firms on Friday said it had the valid licences granted by the government of the Falkland Islands, “and with the full support of the UK government.”

The project is due to deliver its first oil in 2028, Rockhopper and Navitas said the partnerships’ timetable would not be affected.

The Sea Lion oilfield, around 130 miles from the islands, contains an estimated 1.7 billion barrels of oil – described by Rockhopper as a field containing “highly marketable crude”.