Argentina's president has heightened tensions with the UK over the Falkland Islands, warning he will impose economic sanctions on firms which exploit oil close to the British overseas territory.
In a national address, Javier Milei said the "winds of change" favoured Argentina's claim to the islands, emboldened by signs the US might reconsider its stance of neutrality on the issue.
Milei said the Sea Lion oilfield, where a British and an Israeli firm are due to begin exploration work, was a "clear and present danger".
In a statement on Friday, Downing Street said it was "clear that the Falkland Islanders' right of self-determination extends to the right to exploit their own natural resources".
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.
Milei announced his sanctions plan surrounded by his cabinet at the presidential palace, reiterating that the Falklands were "historically and legally" Argentinean.
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.
Defence Secretary Wes Streeting said Britain's commitment to the Falkland Islands is "absolute and unshakeable".
"Milei's statement overnight tells us more about domestic politics in Argentina than it does about the Falkland Islands", he said on X.
On Friday, Downing Street also reaffirmed its position that the islands would remain a British Overseas Territory "for as long as the Islanders wish".
"This is not the first time Argentine governments have made economic threats against the islanders. We are clear that the Falkland Islanders' right of self-determination extends to the right to exploit their own natural resources."
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.
Teslyn Barkman, a former member of the Falkland Islands Legislative Assembly, told the BBC that Milei's speech had "probably irked every single Falkland islander".
Speaking from the capital Stanley, she added that "we have a burgeoning economy for a small place... we will remain forever British".
The crux was a proposal to introduce a bill to parliament to impose sanctions on energy firms planning to begin oil exploration off the Falklands.
The Sea Lion oilfield, around 130 miles from the islands, contains an estimated 1.7 billion barrels of oil - a significant amount.
In comparison, the Rosebank oil field 80 miles west of the Shetland islands in the North Sea, contains an estimated 300 million barrels.
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.
Rockhopper has described the field as containing "highly marketable crude".
In a video posted earlier this year, Navitas highlighted the work it is already carrying out in the Falklands including building a dock, a heliport and accommodation for oil workers.
The BBC has contacted the two companies for responses to Milei's latest comments.
"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.
There is both a domestic and a regional political dimension to this latest escalation on the Falklands.
At home, Milei needs to shore up votes amid his plummeting popularity, currently languishing at around 34%. There is only a year to go before he faces a presidential election and a serious challenge from his erstwhile vice-president, Victoria Villarruel.
A pro-military politician, she has criticised his diplomatic efforts to secure change on the question of Falklands sovereignty. The sanctions may be part of a wider attempt to stave off accusations that he's weak on an issue which is so fundamental to Argentine identity.
It helps Milei that this is about something concrete – the impending oil exploration of an oilfield rather than broad questions of sovereignty and self-determination. He argues that the UK is acting in violation of a UN resolution urging the two sides not to take unilateral action while the dispute remains unresolved.
Milei also announced plans for a naval base in Tierra del Fuego in the south of Argentina, saying Trump and the US were "assessing their historical position in regard to the Falklands", which Argentina refers to as Las Malvinas.
"That is not empty words as they understand that Argentina is a reliable partner and a valuable ally for decades to come," he said, describing the UK as a nation "in decline".
"There are winds of change in the world that are favourable to our claim," Milei added.
When asked in an interview with GB News earlier on Thursday if the US would "come to the UK's aid" during a potential territorial dispute, Trump replied that Britain had "not been there to help me" with his country's war with Iran.
Trump's latest remarks come after he previously said the US position on the Falklands is one of many under review.
Hours before Milei's speech, Sarah Rogers, a senior official in the US state department, posted a photo of herself with Milei alongside the caption: "Exciting things are happening in the Western Hemisphere."
Argentine forces landed on the Falklands to stake a territorial claim in 1982, sparking a 74-day war over the territory as a British military task force ejected them.
The conflict led to the deaths of 255 British military personnel, three islanders and 649 Argentine military personnel.
In a sign of the ongoing tensions between the two countries over the issue, Argentina players celebrated their victory over England in the World Cup by waving a banner in support of their country's territorial claim.
