The King will fly into a Falklands storm on his state visit to America next week.

As Charles prepared for his transatlantic trip, the US threatened to back Argentina's claim to the South Atlantic islands.

Donald Trump is considering withdrawing support for UK sovereignty over the British territory, a leaked Pentagon email revealed. It is one of a raft of controversial measures drawn up to 'punish' Western allies who he deems did too little to support his war with Iran.

The email provoked outrage from British veterans, politicians, and Falklanders, where 99.8 per cent of the population have voted to remain an Overseas Territory of the United Kingdom.

Keir Starmer on Friday vowed that British sovereignty 'isn't going to change', while SAS hero Robin Horsfall said ministers should treat President Trump 'with the contempt and disdain he deserves'.

But Downing Street was unable to say whether the UK was still capable of defending the archipelago given the parlous state of the Navy. Asked twice, Sir Keir's spokesman called it a 'hypothetical' issue.

There are concerns Argentina's hard–Right leader, and Trump ally, Javier Milei could be emboldened by a change in US policy. Just this week, he said he was doing 'everything humanly possible' to claim the islands.

There are currently just four Typhoon fighter jets on the islands along with HMS Medway – a Batch 2 River–class offshore patrol vessel – and 1,200 to 1,500 military and civilian personnel at RAF Mount Pleasant.

In 1982, it took a force of 26,000 men, two aircraft carriers, assault ships, destroyers, frigates, submarines, dozens of fighter jets and bombers to liberate the islands after Buenos Aires invaded. When the RAF base on Cyprus was attacked by Iranian proxies at the beginning of the current Middle East conflict, it took three weeks to get a warship to the Mediterranean.

King Charles and Queen Camilla are due to touch down in Washington DC on Monday ahead of a banquet dinner at the White House the following day.

There had already been calls from the Left for the trip to be cancelled after Mr Trump repeatedly mocked and humiliated Sir Keir for not supporting his military campaign.

An internal memo seen by Reuters floated reassessing US diplomatic support for longstanding European 'imperial possessions' such as the islands.

The US is also considering kicking Spain out of Nato for refusing to let its fighter jets use key bases or even fly in its air space.

British Army veteran Simon Weston, 64, who suffered severe burns during the war, said: 'What it [the Falklands] has to do with Mr Trump, I have no idea.

'He should leave the islanders alone and sort out the problems he created himself. Stop blaming others. He can't be a schoolyard bully. If he's got a dispute with Mr Starmer then deal with Mr Starmer – don't bring the islanders into it.

'The rest of the world is not his toy to play with.'

Mr Trump is making threats after Britain refused to back his Iran war. He has been trying to pressure Nato colleagues into joining his efforts, claiming support should be 'automatic'. The alliance's Article Five treats an attack on one member as an attack on all. It has been invoked only once in 77 years – after 9/11.

President Ronald Reagan refused to come to Britain's aid in 1982, when the 74–day Falklands War saw 255 Britons killed and 775 wounded.

Mr Horsfall, a veteran of both the Falklands and the Iranian Embassy siege, told the Mail: 'It [the Argentine invasion] was an attack on a Nato state and Article Five wasn't invoked.

'Behind the scenes Reagan supported us with a certain amount of material, arms, ammunition, satellite and so on, but they kept out of it.

'Trump's obviously playing some stupid games with King Charles before he gets there. The whole thing is ridiculous.

'I think the visit is a disgrace. I think it's a political disaster. He is going there to be humiliated by this moron. You've got to treat Trump with the contempt and disdain that he deserves.'

Mr Trump told Reuters the topics he will discuss with King Charles next week included Iran, Nato and the UK's digital services tax. Sir Keir's spokesman said: 'We could not be clearer about the UK's position on the Falkland Islands. Sovereignty rests with the UK, and the islands' right to self–determination is paramount.'

International relations expert Professor Peter Clegg said

Mr Milei was 'marginally less uncompromising' than his predecessors, but 'the territorial claim itself remains unchanged'.

He said 'direct US pressure on companies involved in planned activities such as oil exploration could have an effect' in the long run. Tory leader Kemi Badenoch said: 'The Falkland Islands are British. They have been for a very long time. The sovereignty is British sovereignty.'

A Falklands government spokesman said it had 'complete confidence in the commitment made by the UK to uphold and defend our right of self–determination'.