THE US ditching its Nato allies would be "the worst possible case scenario" and would "embolden Vladimir Putin to push into Europe", a former army commander has warned.
As Donald Trump edges closer to snatching back the keys to the White House, it is feared he could fulfil his threat to pull the United States out of the alliance.
The weakening of Nato is one of Putin's greatest desires as the beastly union of the US, Europe and Canada has deterred Soviet and Russian aggression for seven decades.
But Trump - who was at the helm of the US from 2017 to 2021 - could be set for a jaw-dropping return to one of the world's most powerful positions in just nine months.
It has stoked fears the US could leave Nato and leave Europe flailing without its military might and assets worth $3.8 trillion.
European nations in Nato have an agreement to spend 2 per cent of GDP on defence every year.
But in 2018, when Trump was still president, he became so angered by several countries failing to fulfil the quota he threatened to pull out of Nato.
Trump threatened to wash the White House's hands of defending Europe if its own nations can't cough up for its defences.
Days before the chaotic summit in the summer of 2018, Trump, 77, confided in his top national security officials that he did not see the point of the alliance.
He immediately came out brawling once at the gathering in Brussels - accusing a close US ally of being "a captive to Russia".
The Republican also branded member countries "delinquents" in the defence spending and demanded they increase it immediately.
Several countries fell short of meeting the 2 per cent quota during Trump's tenure - and continue to.
According to statistics published by Nato, US military spending in 2023 amounted to 3.49 per cent of GDP.
The UK laid out 2.07 per cent - but Germany, France, Italy and Spain on came up short below the 2 per cent agreed.
And Trump's stance on Nato has not softened since his presidency days.
In chilling remarks earlier this month, the former US leader said he would "encourage" aggressors to "do whatever the hell they want" to Nato allies who do not pay their bills.
At a rally in South Carolina, Trump revealed how he had told a leader he would refuse to protect a nation behind on its payments.
"Well sir, if we don't pay, and we're attacked by Russia - will you protect us?" Trump quoted the unnamed leader as saying.
"I said: 'You didn't pay? You're delinquent?' He said: 'Yes, let's say that happened.' No, I would not protect you. In fact, I would encourage them (Russia) to do whatever the hell they want. You gotta pay," Trump said.
It has reignited fears Trump could attempt to rip the US out of the alliance, should he get back into power.
Colonel Hamish de Bretton-Gordon told The Sun the UK and its allies would be forced to "re-arm at pace" if this happened.
He said: "Without the US, Nato is very much weakened though the arrival of Finland and Sweden is a little compensation."
Mr de Bretton-Gordon warned it could even spur Putin on to expand his invasion and force the UK to deploy troops to Ukraine to hold back a Russian onslaught.
He added: "But the message it would send to Putin is dreadful and would embolden Putin to push harder in Ukraine and ultimately Europe.
"At least the UK and France still have the nuclear deterrent which will give Putin something to think about.
"If this scenario looks likely the UK and other European Nato countries need to re-arm at pace and I expect be prepared to commit boots on the ground in Ukraine to stop Russian advances westwards.
"This is the worst possible case scenario at the moment."
Without the US, Nato would stifle amid the loss of a huge contribution.
The alliance's annual budget and programmes come to around £2.7 billion - with the costs shared.
Between 2021 and 2024, the US has been in the top two contributors, paying just over 16 per cent.
THE North Atlantic Treaty Organisation is a political and military alliance of countries from North America and Europe.
It was founded in 1949 to counter the Soviet Union with Cold War tensions rising.
Among articles in its found treaty is the principle of collective defence - the idea that an attack on one member is considered an attack on all of them.
Nato takes decisions by consensus but the political and military strength of the United States means that it is by far the most powerful country in the alliance.
Its nuclear arsenal is seen as the ultimate security guarantee.
Nato has 31 members - most of them European nations, plus the United States and Canada.
The newest member is Finland, which joined last April in reaction to Russia's 2022 invasion of Ukraine.
Sweden applied to join along with Finland but is waiting for Hungary to ratify its application as the final major step before membership.
The US also has around 85,000 troops throughout Europe, some of whom support non-Nato operations.
And the US defence budget dwarfs every other country in the world.
Last year, America had a whopping $905.5 billion set aside for defence - putting it in the lead by a staggering $700bn.
Russia came in third with $108bn, while the UK trailed behind with $73bn.
France, Germany, Italy and Canada were the only other Nato nations in the top 15, statistics from the International Insitute for Strategic Studies show.
Following Trump's latest disparaging remarks earlier this month, the White House immediately branded them "appalling and unhinged".
A spokesman said it was "encouraging invasions of our closest allies by murderous regimes".
Nato Secretary-General Jens Stoltenberg also hit back at Trump, saying the US leaving Nato would also leave its own troops at risk.
He said: ";Any suggestion that allies will not defend each other undermines all of our security, including that of the US, and puts American and European soldiers at increased risk."
But Nigel Farage has insisted Trump won't abandon Nato or Ukraine.
He said: "There is absolutely no chance of America abandoning their longest, most traditional allies. It isn't going to happen.
"I don't have the view that once Ukraine has fallen that Putin comes for Poland and and the Baltic states - but who knows. I don't have that view, he'd be mad to try and do that."
It comes after Assistant Chief of Staff of Supreme Headquarters Allied Powers Europe (SHAPE), Brigadier General Gunnar Bruegner warned the "clock is ticking" earlier this month.
Without mentioning Russia by name, he said Nato must prove it is "ready" for any threats to its security.
His sobering words came amid a flurry of recent warnings from top military chiefs and policymakers over the threat of full-scale war with Russia in the coming years.
