Argentina's President Javier Milei has said he will sanction oil companies working off the Falklands as he reiterated the country's claim on the British overseas territory in the south-west Atlantic Ocean.
In a national address, Milei said the "winds of change" favoured Argentina's claim to the Falklands, pointing to Washington's readiness to review its neutrality on the dispute.
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".
More than 40 years after the armed conflict over the territory, the sovereignty of the archipelago remains hotly disputed between Britain and Argentina.
BBC News is seeking comment from the UK government on Milei's statement. It reiterated this week that Falkland islanders "are British with a right to determine their own future".
The Sea Lion oilfield contains an estimated 1.7 billion barrels of oil, and production is expected to begin in 2028.
"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.
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.
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 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 could revise its neutral position on the islands' sovereignty if the UK failed to increase defence spending.
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.
"There are winds of change in the world that are favourable to our claim," Milei added.
"I want to be quite clear with everybody. The Falklands are Argentinean. Historically and legally," Milei said.
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.
