The UK's position on the Falkland Islands is "unwavering", Downing Street has said after Argentina's president said the islands were "historically and legally" Argentinian.
Andy Burnham "fully supports the wishes of the islanders to remain a British overseas territory", a Downing Street spokesperson said.
Javier Milei said the "winds of change" favoured his country's claim to the islands and pledged sanctions on firms planning to exploit oil close to the territory.
A British and Israeli partnership due to begin exploration work on the Sea Lion oilfield said it didn't expect recent developments to affect its work in the region.
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.
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."
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".
A very quick guide:
The Falkland Islands
Key facts about the islands and their history
Where are they?
The Falkland Islands are a group of islands in the south-west Atlantic.
There are two main islands, East Falkland, which includes the capital Stanley, West Falkland, and roughly 780 smaller islands and islets.
It is an overseas territory of the UK roughly 8,000 miles from the British Isles and 300 miles from Argentina.
Who lives there?
Around 3,100 people live on the islands.
More than 2,500 live in Stanley with smaller settlements dotted across the main islands and further afield.
Islanders are British citizens and the predominant language is English.
Who governs them?
The Falkland Islands are largely self-governing, although foreign affairs and defence matters are handled by the British government.
The territory has a legislative assembly, which passes legislation, and an executive council, which makes decisions over policy and is chaired by the British governor.
Argentina also claims sovereignty over the islands, calling them Islas Malvinas.
The country says it inherited the islands following its independence from Spain.
Key dates in the Falklands' history
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1690: English captain makes first recorded landing on Falklands
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1764: First settlement founded on East Falkland by French navigator
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1765 British settle West Falkland. They are driven off by the Spanish in 1770 but return in 1771, only to withdraw again in 1774
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1820: Independent Argentina proclaims sovereignty over the Falklands
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1833: British force expels remaining Argentine officials from the island and installs a governor
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1982: Start of Falklands War
What was the Falklands War?
Argentina invaded the Falklands and other nearby British islands in 1982.
After 10 weeks of conflict, British troops recaptured Port Stanley and Argentinian soldiers surrendered.
It led to the deaths of of 655 Argentine and 255 British service personnel, as well as three civilians.
What’s the current situation?
In a referendum held by the Falkland government in 2013, 99.8% of the voters supported remaining an overseas territory of the UK.
Successive British governments have long maintained that Falklanders have a right to self-determination under international law established by the United Nations Charter.
In April 2024, Argentina's President Javier Milei said he would set out a "roadmap" for the islands to become part of Argentina, adding that it would only be achieved via diplomatic means.
On Thursday, President Trump hinted the US would not help the UK in any future Falklands conflict because Britain "had not been there to help me" during his war with Iran.
Trump's latest remarks on the islands come after he previously said the US position on the Falklands is one of many under review.
On Friday, Foreign Secretary Ed Miliband said the UK would "resolutely uphold" the self-determination of the islands.
Writing on X on Friday, Miliband said the Islands would remain British as that is the "overwhelming position of the islanders."
Defence Secretary Wes Streeting also said Britain's commitment to the Falkland Islands was "absolute and unshakeable".
"Milei's statement overnight tells us more about domestic politics in Argentina than it does about the Falkland Islands," he wrote in his own post on X.
In an earlier statement, Downing Street said it was "not the first time" the Argentine government had made economic threats against the Falkland Islands.
"We are clear that the Falkland Islanders' right of self-determination extends to the right to exploit their own natural resources," it said.
