Argentina’s president has said he will impose sanctions on oil drilling off the Falkland Islands as tensions between the UK and Argentina boil over.

In a highly anticipated address, Javier Milei said the “winds of change” favoured Argentina’s claim to control over the British territory, an apparent reference to the US’s willingness to review its position on the dispute.

Milei said Argentina would boost efforts to levy penalties not only against the companies involved in drilling off the Falklands, but also against their shareholders, directors ⁠and suppliers, saying such operations represented a “clear and present danger” to Argentina.

He pledged to boost defence resources to ‌build a naval base in the nearby Tierra ‌del Fuego province, and send Congress an urgent “national sovereignty defence” bill aimed at strengthening Argentina’s ⁠response to what he called unauthorised operations around the islands.

The drilling off the Falklands is led by two British and Israeli companies, which own the Sea Lion oil field containing 1.7 billion barrels of oil.

Milei said Argentina had determined that the Sea Lion offshore project, operated by Navitas Petroleum and Rockhopper Exploration, could begin oil development in the coming months, creating an urgent threat to Argentine interests.

“If we do not act swiftly, in a few months they will have the material capacity to access the oil that lies underneath our sea – something that has never happened before,” Milei said.

In a statement on X earlier this week, Argentina’s president said the islands – which Argentina calls the Malvinas – were “sacred” and his country’s national sovereignty had been “violated”.

He wrote: “What more important and strategic cause for the vital interests of the nation could there be more important than the Malvinas cause?… We will continue defending the interests of the Argentine nation with tooth and nail, no matter who it bothers. LONG LIVE FREEDOM, DAMMIT…!!!”

On Tuesday, Downing Street said Britain’s commitment to the Falkland Islands was “unwavering”.

James Cartlidge, the shadow defence secretary, hit back at President Milei, saying the Falklands “are British and they will remain British”.

“British soldiers fought and died to defend our sovereignty and the freedom of the Falkland Islanders. That sacrifice will never be forgotten, and we will always stand by the people of the Falklands and their overwhelming desire to remain British,” he said.

US president Donald Trump suggested he would not back the UK if Argentina invaded the Falkland Islands, in response to the UK’s stance on the Iran war. He told GB News: “Your country was not there to help me.”

Falkland Islanders voted overwhelmingly to remain a British overseas territory in a 2013 referendum, with 99.8 per cent voting in favour – and just three votes against.

But the issue hit the headlines this summer when Argentina’s football team controversially waved a banner in support of their country’s claim to the islands while celebrating their World Cup win against England.

Players held a banner after the semi-final match that read “Las Malvinas son Argentinas”, which translates as “The Falklands are Argentine”.